Abstract: The present invention is a method of combustion of a solid fuel stream with oxygen. The present invention includes introducing a first stream, comprising a first portion of substantially pure oxygen, into a first conduit. The present invention includes introducing a second stream, comprising a solid fuel stream and a conveying media, into a second conduit, wherein the second conduit is concentric with, and surrounding, the first conduit. The present invention includes introducing a third stream, comprising a second portion of substantially pure oxygen, into a third conduit, wherein the third conduit is concentric with, and surrounding, the first conduit and the second conduit. The present invention includes igniting the first stream, the second stream, and the third stream as they exit the first conduit, the second conduit and the third conduit, in such a way as to create a flame.

Abstract: A combustion system equipped with one or more carbonaceous fuel burning combustors (e.g., slagging Cyclone combustor) and adapted to minimize nitrogen oxide (NOx) formation during staged combustion operation by selective introduction of oxygen through at least one of the combustors to create a hot sub-stoichiometric combustion zone by reducing the diluent effect of nitrogen and other inert gases present in the oxidizer/air. A method of operating the combustion system of the invention with reduced NOx emissions is also disclosed.