Study on High Temperature Corrosion Performance of Biomass Boiler Superheater and Protective Measures

Abstract

Aiming at the problems of pressure - bearing pipes thinning and even rupture caused by the high temperature corrosion of the biomass boiler superheaters, the microstructure and properties of superheater tube wall after service were analyzed based on working environment. Research results showed that elements such as Cl and alkali metals in the flue gas underwent a series of complex physical and chemical reactions with the heating surface in the form of gas, solid and liquid phases at high temperatures, resulting in the corrosion of the superheaters pipe wall. The fly ash was deposited on the metal surface and soakably adhered to the oxide layer, which made the oxide protective layer on the pipe wall surface fell off, leading to the thinning of the pipe wall. Meanwhile, the service temperature of the high temperature superheaters was higher than that of the medium temperature superheater, and the corrosive peeling of its oxide layer was more serious. After long - term service, the micro hardness and tensile property of the pipe wall of the high temperature superheater after corrosion was decreased, compared with that of the medium temperature superheater. But, both of them still met the standard requirements and service conditions. Therefore, taking appropriate protective measures was able to prevent further corrosion and thinning of the pipe wall, which could shorten the maintenance period and reduce operating costs.

Keywords

• biomass boiler|superheater|high temperature corrosion|mechanical property|protective measure