Materials exposure test results and post-test examination of construction materials used in HYCOL coal gasification pilot plant

This paper describes the corrosion test results obtained from the field exposure test of commercial alloys for about 2100 hours. Post-test examination of various construction materials used in HYCOL coal gasification pilot plant was also included. Materials exposure tests were carried out in the heat recovery boiler section with uncooled coupons located at four different temperature zones from 400 to 700 degrees C. Alloys with Cr contents greater than 12% performed best in the all test conditions. Corrosion losses of the specimens used in tests with frequent downtime were found to be higher regardless of their Cr contents. Various pilot plant components were inspected at the site from the material standpoint of view after the completion of the planned performance tests, some of which were cut out and analysed in the laboratory. The major causes of damages of the metallic materials observed by post-test examination were sulfidation-oxidation of the heat exchanger tubes during high temperature operation, and dew point or downtime corrosion such as intergranular cracking and pitting. Refractory materials for the gasifier had been deteriorated by dissociation related with molten slag penetration.