A 600 MW unit in Laoz applies octagonal corner tangentially-fired boiler with design coal of low heat value lignite coal.The load increase or decrease rate of this unit is higher than the actual load change rate of the similar 600 MW units in China.Due to such reasons as the low volumetric heat release rate of the boiler

limited grinding ability of the coal mill

large size of coal particles and lack of effective regulation on coal fineness

several problems occurred in this unit

like high stable load without diesel oil support

large amount of carbon content in the bottom slag

poor flame stability

and so on.Thus

combustion adjustment measures like the secondary air flow distribution test and coal mill combination changing were performed

to improve the combustion conditions.The results show the combustible matter content in the bottom slag reduced from 28.28%to 15.10%

in the fly ash dropped from 0.83%to 0.63%

and the unburned carbon heat loss decreased from 2.54% to 1.45%.The mechanical incomplete combustion heat loss reduced

indicating the energy saving effect is dramatic.