Carbon-rich gases interacting disastrously with high-temperature alloys: Metal Dusting

摘要

Process operators keep pushing the conditions towards material limits. Plant engineers and materials engineers try to move these limits in order to prevent failures. In some cases however, it is not known how materials will respond to change of conditions, moreover expected milder conditions might very well be more aggressive if the considered corrosion process is not well understood and/or characterised. One of these cases is Metal Dusting (MD). As long as a solid physical/chemical explanation of the phenomenon metal dusting is not available, testing is very important. The theory is not able to predict or prevent metal dusting, nor based on the material science, nor on the basis of gas chemistry Therefore, it is needed to test materials for metal dusting prone applications in a close-to-practice way, such that an indication can be given of the metal dusting aggressivity of a gas, and of the metal dusting sensitivity 9f a material. The test rigs and procedure as being developed at TNO have seen to reduce the testing time to 1000 - 2000 his in order to come to a conclusion about the MD behaviour. It has seen to be of uttermost importance to perform testing close to practice, because it has been seen difficult to accurately predict the behaviour from theory, or from tests with far diverting conditions. This addresses temperature, pressure as well as gas composition. The tests at TNO as performed during this programme has seen to give results which were in good comparison with in-plant exposure results.