Abstract: 670 MW supercritical once-through boiler roof adopts twice sealing forms, and guard plate material is heat-resisting, anti-corrosive, ductility material. However, due to the oversized ceiling area and complex expansion, guard plate is easily to be ripped; besides, the heat-resisting plastic and refractory castable material will become loose due to heat, which will lead to flue emission. In order to solve the problems and increase the boiler efficiency, on the base of twice sealing forms, environmental nonmetallic three-dimensional flexibility seal technology is adopted, and the boiler furnace top seal situation is modified. It is not only solving flue gas leakage, ash leakage ,but also improving boiler efficiency and unit operation environment.

Key words: ash leakage, chinaware fiber, nonmetallic tridimensional flexible seal technology, expansion