NOx reduction in combustion with concentrated coal streams and oxygen injection

A method of combustion, comprising providing a feed stream of pulverulent solid hydrocarbonaceous fuel in a gaseous carrier,

• obtaining from said feed stream at least one obtained stream comprising said fuel and said carrier and having a ratio of fuel to carrier that is higher than the ratio of fuel to carrier of said feed stream,
• feeding said obtained stream and air from a burner to a combustion chamber, injecting oxygen into said obtained stream at or near said burner, and combusting the coal in said obtained stream in said combustion chamber with said air and oxygen in a flame that has a fuel-rich flame zone, wherein the amount of said oxygen is less than 25% of the stoichiometric amount required for complete combustion of said fuel and keeps the zone fuel-rich, while reducing the amount of air fed through said burner by an amount containing sufficient oxygen that the overall combustion zone stoichiometric ratio varies by not more than 10% compared to the stoichiometric ratio without said addition of oxygen.