Reducing the minimum load and NOx emissions for lignite-fired boiler by applying a stable-flame concept

For the purpose of improving the load range and NOx emission level of lignite-fired power plants, a new combustion technology, called NR-LE burners (NOx Reduction-Load Extension), has been developed in co-operation between Babcock-Hitachi and Fortum. A single-burner combustion test was performed in Japan with this new NR-LE type burner using Czech lignite. Adapting the flame-stabilization ring and a special additional air-nozzle resulted in achieving a stable flame, which enables: • The burner minimum load to be less than 50% (Boiler load: 30–40%) • Low NOx emissions of less than 200 mg/m3 (6% O2, dry base) The first commercial full-scale application of the NR-LE burner was by the IPP power producer in the Czech Republic (Sokolovská Uhelná, a.s. at Vresová Unit2 boiler with steam parameters 325 t/h, 535 °C, 13.5 MPa). The commissioning test runs of the new burners were carried out during September to October 2001. The boiler is now in commercial operation, with (i) a 30% minimum load without supplementary fuel, and (ii) lower NOx emission levels.