Method for operating a slag tap combustion apparatus

The present invention provides a method of operating a solid fuel fired boiler comprising introducing a solid fuel and an iron-bearing material into the boiler. The solid fuel is at least partially combusted in the boiler to produce an ash slag, wherein the ash fusion temperature characteristics (i.e., one or more of the IDT, ST, HT, and FT) of the ash slag are different than the ash fusion temperature characteristics of the ash slag that would result on combustion of the solid fuel alone. The method of the present invention is particularly applicable to slag tap boilers, including cyclone-type boilers. These boilers are, typically, designed to operate with a liquid ash slag.The iron-bearing material may be, but is not limited to, at least one of iron ore beneficiation tailings, iron ore fines, pelletized blends of coal and iron-bearing material, pelletized solid fuel containing iron-bearing compounds, iron-bearing boiler ash, mill scale from steel production, dust from blast furnace gas cleaning equipment, flue dust from sinter plants, and other materials including iron or including material that bears iron. According to the present invention also describes methods of introducing the iron-bearing material into the slag tap combustion apparatus. The method of the invention allows lower sulfur coals, as well as other fuels typically unsuited for use in slag top boilers, to be used in such boilers, significantly reducing SO2 emissions.