Chemical cleaning of ultra-supercritical boilers with austenitic superheaters

Formation of a thin, dense magnetite layer on the inner surfaces in the evaporator and superheater tubes is of vital importance for an ultra-supercritical boiler. This can be obtained only if all internal surfaces have been chemically cleaned before commissioning and if the boiler is operated with optimal water and steam purity. The chemical cleaning comprises acid cleaning of all heat surfaces in the boiler including acid cleaning of the austenitic superheaters. In this regard, the boiler manufacturer FLS Miljo/Burmeister & Wain Energy and the chemical cleaning company Hans Wistrand AB have undertaken a laboratory tests, as well as the full scale acid cleaning.