The boiler uses the way of circulation fluidized bed combustion, having high firing efficiency and lower pollution. The fuel such as coal slime and coal waster has lower calorific value, but the combustion efficiency reaches up to 97%. If the fuel had high content of sulfur, adding limestone into furnace can obviously reduce sulfur dioxide emission, meanwhile, firing temperature of 900℃ is able to control NOx emission and to lessen corrosion and pollution caused by flue gas. The slag can be an additive of cement.