Investigation of Radiometric Combustion Monitoring Techniques for Coal- Fired Stoker Boilers

Fuel-ash bed disturbances are costly problems often encountered in operating coal-fired, mechanical-stoker boilers in military heat plants. In traveling grate, mechanical-stoker boilers, all or most of the coal burns on the traveling grate, so proper control of combustion grate fuel-ash bed thickness is critical for cost-effective, high-availability operation. In these plants, operators must adjust combustion equipment as the coal enters the combustion chamber. Because fuel bed problems take several minutes to develop, operators may not discover problems before they go past the point of easy correction. This study investigated the use of a remote sensing system to monitor conditions in the fuel bed. It is concluded that the technology to measure mechanical stoker boiler fuel-ash bed temperatures by radiation techniques is sufficiently developed to produce a fuel-ash bed temperatures-monitoring system. Such a system may significantly reduce fuel-ash bed disturbances by detecting bed temperature changes that indicate the onset of bed entrainment and clinker formation. Continuous, reliable measurement of fuel-ash bed temperatures could also detect smoking and conditions leading to smoking, and could be used to improve boiler efficiency through improved control of excess air.