Based on the variability of coal types used in thermal power plants

the unit parameters before and after changing coal blending scheme in Hepo supercritical 350MW circulating fluidized bed boiler were compared. The influence of coal variation on the boiler operation was analyzed from several aspects

such as air chamber pressure

furnace differential pressure

bed temperature

heating surface parameters

mass ratio of fly ash to bottom slag

NO_x emissions

and coal ash formation characteristics. The results show that

after blending with anthracite from Huanghou mine

the bed temperature increased by an average of 17～27 ℃ and the amount of desuperheating water increased. Besides

the furnace differential pressure decreased by nearly 30% on average and the amount of circulating ash also reduced. Moreover

the discharge slag and the carbon content of fly ash and bottom slag increased

but the NO_x generation amount reduced. The anthracite has low ash content

large calorific value

low attrition rate and poor ash formation characteristics

which will cause changes in material balance characteristics and heat transfer characteristics. Therefore

it is recommended to keep relatively high bed pressure to maintain the load capacity and control the fed-coal particle size to be finer

that is

to increase the mass proportion of particles with size of 500～3200μm and reduce the mass proportion of the maximum particle size range

thus to extend the selection of coal types for circulating fluidized bed boilers and reduce the fuel costs.