Solid fuel and oxygen combustion with low NOx and efficient burnout
Solid particulate fuels are combusted with a primary oxidant stream of industrially pure oxygen and a secondary oxidant stream of industrially pure oxygen optionally mixed with a portion of recycled flue gas. The fuel is conveyed with a carrier gas of air or recycled flue gas. An oxygen concentration out of the total amount of the fuel stream and the primary and secondary oxidant streams is 40-63% by mass or 47-70% by volume.
1. A method for combustion of a solid fuel with low NO x emissions and satisfactory burnout, comprising the steps of:
supplying a flow of a primary oxidant from a first nozzle, the primary oxidant being industrially pure oxygen;
supplying a flow of fuel from a first annulus disposed between the first nozzle and a second nozzle disposed concentrically around the first nozzle, the fuel being particulate coal and a carrier gas;
supplying a flow of a secondary oxidant from a second annulus surrounding and coaxial with the second nozzle;
combusting the fuel and primary and secondary oxidants to produce flue gas; and
collecting and recycling a portion of the flue gas, wherein:
the secondary oxidant is industrially pure oxygen mixed with a portion of the recycled flue gas, the recycled flue gas constituting 18.2-47.1% (vol/vol) of the secondary oxidant and the oxygen constituting the balance of the secondary oxidant;
the carrier gas is a portion of the recycled flue gas;
the primary oxygen is 2.7-10% (vol/vol) of the amount of oxygen in the flows of primary oxidant and secondary oxidant;
a total amount of oxygen in the flows of primary oxidant, secondary oxidant, and fuel is 47% to 70% (vol/vol); and
the percent burnout of the particulate coal being greater than 97.25% and less than 99.5%.