A process for mitigation of fouling deposits within a combustion zone, capturing of toxic metal emissions, and reduction of visible sulfur emissions attributable to sulfuric acid mist during coal combustion. SO.sub.3 formed during coal combustion is reduced by the addition to the coal of raw, unprocessed magnesium-containing minerals such as magnesite ore or brucite ore. The minerals are pulverized to a fine particle size and combined with pulverized coal to provide a mixture of the particles. The mixture is combusted and the ore particles calcine and decrepitate to very fine magnesium oxide particles that have a significant particle surface area. The magnesium oxide particles react with the SO.sub.3 produced during combustion of the coal and also capture toxic metals to reduce the quantity of undesirable stack discharge components.