Erosivity of particles in circulating fluidized bed combustors

The metal wastage of superheater tubes in the convection pass region of circulating fluidized bed combustors is a current problem. An investigation was carried out to determine what kinds of metal loss rates and mechanisms occurred when the various types of particles from two circulating fluidized bed combustors were used as erodents in a laboratory blast nozzle tester. The laboratory tests were compared with in-service exposures. A loss mechanism was established that was based on metal losses and the observed microstructures of eroded-corroded surfaces. It was determined that the particles must be strong enough not to shatter upon impact in order to be erosive and that more angular and larger size particles have higher erosivities. The laboratory and in-service loss mechanisms were determined to be similar.