Waterwall corrosion after combustion modifications for NOx control
Much of the information concerning the mechanisms contributing to waterwall corrosion in coal fired boilers has been derived from examination of tube/deposit sections collected after the boiler has been taken out of service. In some circles this is referred to as the cut, polish and guess approach. The potential problems associated with staged combustion were recognized when it was first proposed for coal fired boilers. There were concerns about reduced thermal efficiency due to the presence of unburned carbon and the potential for increased waterwall corrosion rated in the lower furnace which is subjected to sub-stoichiometric conditions. Developers claimed that unburned carbon was not a problem and improving coal particle fineness would reduce unburned carbon. Field tests had often shown no significant increase in tube wastage rates. Yet recent experience with plants that have been retrofitted with advanced low-NO{sub x} firing systems is contrary to this optimistic view. Almost invariably, carbon in the fly ash increases and several plants are reporting excessive waterwall wastage tube rates after retrofitting low-NO{sub x} firing systems. Regardless of the reasons, in-furnace NO{sub x} control technologies may not be a low cost panacea for more stringent NO{sub x} emission limits as was originally thought. This paper describes the use of a reacting, computational fluids dynamic model to simulate boilers fitted with advanced low-NO{sub x} firing systems to investigate the link between firing system characteristics and the conditions that might affect waterwall corrosion such as local hydrogen sulfide concentration, heat flux, etc. The model does not predict corrosion directly unless the corrosion rate can be linked to the predicted properties.
- Research Organization:
- Reaction Engineering International (US)
- OSTI ID:
- 20013461
- Resource Relation:
- Conference: 24th International Technical Conference on Coal Utilization and Fuel Systems, Clearwater, FL (US), 03/08/1999--03/11/1999; Other Information: PBD: [1999]; Related Information: In: The proceedings of the 24th international technical conference on coal utilization and fuel systems, by Sakkestad, B.A. [ed.], 1091 pages.
- Country of Publication:
- United States
- Language:
- English
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