On-line coal flow measurement for improved boiler performance

More stringent emission limits or the addition of post combustion NOx control create the need for improvements of NOx emissions from pulverized coal boilers. Even boilers retrofitted with Low NOx technology during Phase 1 and Phase 2 of the CAAA are required to reduce emissions for compliance or total cost considerations. Technical solutions range from addition of overfire air and state-of-the-art low NOx burners to low cost additions of combustion enhancements. Regardless of the combustion NOx control method used, stoichiometries local to the burners must be maintained at the designed values at all times to provide high NOx performance at low efficiency loss due to unburned fuel. A proper air and coal balance at the burners is the key issue for these advanced systems. This paper describes Foster Wheeler's approach to NOx emission improvements for existing low NOx firing systems. The ECT technology to measure coal flow individually for each burner and to control the parameters for optimum combustion are presented and discussed. Field experience shows the installation and advantages of the technology.