On-line carbon-in-ash monitors: Survey and demonstration

Fly ash unburned carbon (UBC) level is an important consideration for combustion efficiency as well as ash marketing. The presence of unburned carbon in fly ash has been shown to be a function of furnace design, coal quality, the ability of the pulverizer to grind the coal, and heat release rate. Boilers are designed to take these factors into consideration. However, the Clean Air Act Amendments of 1990 drove many utilities to switch coal supplies and install low NO{sub x} burners. Higher carbon-in-ash levels have been the result of these changes in coal quality and the staged combustion characteristics associated with low NO{sub x} burners. Over the past few years, several instruments for the on-line determination and monitoring of the unburned carbon content of ash samples have been developed. However, to date they have not been deployed widely in the U.S. despite potential uses for combustion optimization and as an aid in fly ash marketing. Based on the lack of publicly available performance and operation data available for the current CIAM (carbon-in-ash monitor) commercial offerings, Southern Company initiated a demonstration of several commercial technologies on its coal-fired units. As part of a DOE Clean Coal Project demonstrating advanced wall-fired combustion techniques for the reduction on NO{sub x} emissions from coal-fired boilers, the CAM, SEKAM and FOCUS systems were installed at Georgia Power Company`s Plant Hammond Unit 4. CAM and M&W instruments were also placed at Alabama Power Company`s Plant Gaston Unit 4. The testing of the instruments was conducted from November 1995 through August 1996