Real-Time Monitoring of Unburned Carbon on Utility Fly Ash

This paper discusses the application of on-line LOI (or carbon-in-ash) analyzers to utility boilers for the purpose of optimizing firing system and thermal performance while maximizing the revenue from fly ash sales. Fly ash value is strongly affected by the unburned carbon content. Fly ash sample collection philosophy and unburned carbon measurement technology will be briefly reviewed. Several installations from around the world using a multiple sampling point, microwave based system will be described and improvements to plant operation discussed. Special emphasis will be placed on commercial installations and use of the technology in the United States. The installations cover a variety of boiler and firing system designs as well as a range of fuel characteristics.