Corrosion in syngas coolers of entrained slagging gasifiers

The corrosion of candidate alloys and coatings for syngas coolers is studied in the laboratory prior to testing and use of materials in pilot plants. In many cases, simulated syngas tests in the laboratory have not reproduced adequately the attack that has been observed in pilot plant exposure of the same materials. A study of the process variables that may influence corrosion has been made to determine what modifications of laboratory tests can be introduced to reproduce more accurately the results of plant exposures. Variables that have been evaluated include: (1) cyclic operation, (2) temperature differential between gas and metal surfaces, (3) H{sub 2}S partial pressure and total system pressure, (4) applied stress, (5) HCl in syngas, and (6) surface deposits of slag and chlorides. Results indicate that each variable has a significant effect on the behavior of one or more materials that are being considered for use in operating plants. Several variables have a significant effect only when they are coupled together. The relative importance of the test variables is strongly materials dependent. The in-plant behavior of most materials can be reproduced accurately by modification of laboratory tests to include these variables. Testing at atmospheric pressure under isothermal conditionsmore » is suitable for screening of materials but fully integrated testing under high pressure syngas with HCl, surface deposits, and a temperature differential between the gas and metal is recommended for an in-depth evaluation of the most promising materials. 23 refs., 71 figs., 16 tabs.« less