Minimization of NOx emissions and carbon loss in solid fuel combustion

A method of decreasing concentration of nitrogen oxides and carbon loss in a combustion flue gas comprising:

• a) providing a boiler having a combustion zone;
• b) providing a plurality of burners in a lower level of said combustion zone and one or more burners in an upper level of said combustion zone;
• c) injecting combustible solid fuel and an oxidizing agent into said plurality of burners in the lower level of said combustion zone;
• and
• d) injecting partially gasified solid fuel into at least one of said one or more burners in said upper level of said combustion zone;
• wherein said partially gasified solid fuel is separated into combustible volatiles and char prior to step d), and the char is subsequently conveyed to said plurality of burners in the lower level of said combustion zone.

A method of decreasing concentration of nitrogen oxides and carbon loss in a combustion flue gas comprising:

• a) providing a combustion zone including a primary zone, a reburning zone and a burnout zone;
• b) providing a plurality of burners in the primary zone;
• c) injecting a combustible solid fuel and an oxidizing agent into said plurality of burners in the primary zone;
• d) partially gasifying solid fuel particles in a duct upstream of said one or more burners by mixing the solid fuel particles with recycled flue gas at a temperature of 600-900° F.;
• and
• e) injecting partially gasified coal into said reburning zone, downstream of said primary zone.

A method of decreasing concentration of nitrogen oxides and carbon loss in a combustion flue gas comprising:

• a) providing a combustion zone including a primary zone, a reburning zone and a burnout zone;
• b) providing a plurality of burners in the primary zone;
• c) injecting a combustible solid fuel and an oxidizing agent into said plurality of burners in the primary zone;
• and
• d) injecting partially gasified coal into said reburning zone, downstream of said primary zone;
• wherein said partially gasified solid fuel is separated into combustible volatiles and char prior to step d), and the char is subsequently conveyed to one or more of said plurality of burners in said primary zone.

A method of decreasing concentration of nitrogen oxides and carbon loss in a combustion flue gas comprising:

• a) providing a boiler having a combustion zone;
• b) providing a plurality of burners in a lower level of said combustion zone and one or more burners in an upper level of said combustion zone;
• c) injecting coal and an oxidizing agent into said plurality of burners in said lower level of said combustion zone to produce a combustion flue gas;
• d) partially gasifying solid fuel particles in a duct upstream of said one or more burners by mixing the solid fuel particles with recycled flue gas at a temperature of 600-900° F.;
• and
• e) injecting partially gasified coal into at least one of said one or more burners in said upper level of said combustion zone.

Apparatus for minimizing NOx emissions and carbon loss in solid fuel combustion comprising:

• a boiler having an inlet, a combustion zone, and an outlet;
• a plurality of burners arranged in a lower level of said combustion zone and one or more burners in an upper level of said combustion zone;
• means for supplying air and solid fuel to said plurality of burners in said lower level of said combustion zone;
• partially gasifying solid fuel particles in a duct upstream of said one or more burners in said upper level of said combustion zone by mixing the solid fuel particles with recycled flue gas at a temperature of 600-900° F.;
• and
• injecting the partially gasified solid fuel into at least one of said one or more burners in said upper level of said combustion zone.

Apparatus for minimizing NOx emissions and carbon loss in solid fuel combustion comprising:

• a boiler having an inlet, a combustion zone, and an outlet;
• a plurality of burners arranged in a lower level of said combustion zone and one or more burners in an upper level of said combustion zone;
• means for supplying air and solid fuel to said plurality of burners in said lower level of said combustion zone;
• means for supplying partially gasified solid fuel to at least one of said one or more burners in said upper level of said combustion zone, including a cyclone separator upstream of said at least one burner in said upper level of said combustion zone for separating said partially gasified solid fuel into volatiles and char;
• and
• means for supplying the char to said plurality of burners in said lower level of said combustion zone.

Apparatus for minimizing NOx emissions and carbon loss in solid fuel combustion comprising:

• a boiler having an inlet, a combustion zone, and an outlet wherein said combustion zone includes a primary zone, a reburning zone and a burnout zone;
• a plurality of burners arranged in said primary combustion zone;
• means for supplying air and solid fuel to said plurality of burners in said primary zone;
• means for supplying partially gasified solid fuel to said reburning zone, including means for separating solid residue from said partially gasified solid fuel and supplying said solid residue to at least one of said plurality of burners in said primary zone;
• and
• means for supplying the char to said plurality of burners in said primary combustion zone.