Abstract: The generation of clinker ash from exhaust gas dust in a boiler, furnace or the like which employs dust coal as a fuel can be controlled with excellent results by adding to a fuel at least one iron compound in a relatively small amount, and, preferably, at least one compound of a metal selected from the group consisting of Cu, Mn, Co, Ni and Cr, and, preferably, at least one compound of a metal selected from the group consisting of an alkali metal and an alkaline earth metal, in the form of an aqueous solution or a water slurry in which the particles are capable of passing through a 100-mesh screen.

Abstract: The deactivation of a denitrating catalyst that is caused by exhaust gas dust in a boiler, a furnace or the like which employs a fossil fuel, particularly pulverized coal, can be controlled with excellent results by adding to a fuel at a mill installed in a coal fuel line or at a point upstream of the mill at least one iron compound in a small amount in the form of an aqueous solution, or a powder or water slurry containing coal particles, or in case of employing pulverized coal or heavy oil as a fuel by adding a mixture of an iron compound, a vanadium compound and a tungsten compound, said mixture being in the form of powder, a water slurry or an oil slurry of powder, or an aqueous solution.