Abstract: The following specification discloses a process and burner for combusting fossil fuels such as coal to provide low SO.sub.x and NO.sub.x emissions. The process includes pulverizing the coal together with an alkaline material, such as limestone in an amount calculated to provide an alkaline metal stoichiometric equivalent of one to seven times the stoichiometric equivalent of the sulphur contained in the coal. The resulting pulverized coal-limestone mix is then combusted under fuel rich conditions. For example, 25% of the theoretical air required to combust the coal is preheated and injected into the combustion zone together with the pulverized coal-limestone mixture. The primary or transport air is swirled to increase mixing and to stabilize the flame. Preheated secondary air is introduced to the combustion zone. The amount of the preheated secondary air amounts to approximately 40% to about 100% of the theoretically required air.