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A burner assembly cofires a primary solid fuel and a secondary solid fuel in a combustion zone of a boiler. The burner assembly includes a fuel injector that mixes the primary solid fuel and the secondary solid fuel prior to injection into the combustion zone of the boiler. The primary solid fuel ma

A burner assembly cofires a primary solid fuel and a secondary solid fuel in a combustion zone of a boiler. The burner assembly includes a fuel injector that mixes the primary solid fuel and the secondary solid fuel prior to injection into the combustion zone of the boiler. The primary solid fuel may be pulverized coal, pulverized petroleum coke, or the like, while the secondary solid fuel may be a biomass fuel or refuse-derived fuel.

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What is claimed is: 1. A fuel injector comprising: a primary inlet port for receiving a primary solid fuel; a secondary inlet port for receiving a secondary solid fuel; a mixing chamber including a mixing element within said fuel injector arranged downstream of the primary and secondary inlet por

What is claimed is: 1. A fuel injector comprising: a primary inlet port for receiving a primary solid fuel; a secondary inlet port for receiving a secondary solid fuel; a mixing chamber including a mixing element within said fuel injector arranged downstream of the primary and secondary inlet ports for mixing intimately the primary solid fuel and the secondary solid fuel to provide a substantially homogenous mixed solid fuel, the mixing element being a diffuser or an impeller; and a nozzle arranged downstream of the mixing chamber at a distal end of the fuel injector for providing the mixed solid fuel to a combustion chamber. 2. The fuel injector of claim 1, wherein the fuel injector is a scroll-type. 3. The fuel injector of claim 1, wherein the fuel injector is a elbow-type. 4. The fuel injector of claim 1, wherein the fuel injector includes an impeller for intimately mixing the primary solid fuel and the secondary solid fuel. 5. The fuel injector of claim 1, wherein the fuel injector includes a diffuser element for intimately mixing the primary solid fuel and the secondary solid fuel. 6. The fuel injector of claim 1, wherein the primary solid fuel is pulverized coal. 7. The fuel injector of claim 1, wherein the primary solid fuel is petroleum coke. 8. The fuel injector of claim 1, wherein the secondary solid fuel is a biomass fuel. 9. The fuel injector of claim 8, wherein the biomass fuel is predryed. 10. The fuel injector of claim 1, wherein the secondary solid fuel is petroleum coke. 11. A fuel injector for use in a furnace, the fuel injector comprising: a first inlet for receiving a primary solid fuel; a second inlet for receiving a secondary solid fuel; at least one elongated barrel connected to the first inlet or the second inlet; a mixing chamber connected to the at least one elongated barrel for mixing the primary solid fuel with the secondary solid fuel; and a nozzle at a distal end of the fuel injector for providing the mixed primary solid fuel and the secondary solid fuel to a combustion chamber. 12. The fuel injector of claim 11, wherein at least one of the first inlet and the second inlet is a scroll-type inlet. 13. The fuel injector of claim 11, wherein at least one the first inlet and the second inlet are elbow-type inlets. 14. The fuel injector of claim 11, wherein the mixing chamber includes a mixing element for mixing together the primary solid fuel and the secondary solid fuel. 15. The fuel injector of claim 14, wherein the mixing element is a diffuser element. 16. The fuel injector of claim 14, wherein the mixing element is an impeller. 17. The fuel injector of claim 11, wherein the primary solid fuel is pulverized coal. 18. The fuel injector of claim 11, wherein the primary solid fuel is petroleum coke. 19. The fuel injector of claim 11, wherein the secondary solid fuel is a biomass fuel. 20. The fuel injector of claim 19, wherein the biomass fuel is predryed. 21. The fuel injector of claim 11, wherein the secondary solid fuel is petroleum coke. 22. A cofiring burner system comprising: a furnace; at least one primary feed pipe for providing a primary solid fuel; at least one secondary feed pipe for providing a secondary solid fuel; and at least one fuel injector abutting the furnace for mixing the primary solid fuel and the secondary solid fuel within the fuel injector and for providing the mixed fuel to the furnace for combustion therein, the at least one fuel injector being a scroll-type or elbow-type of fuel injector. 23. The cofiring burner system of claim 22, wherein the fuel injector includes a mixing element for mixing the primary solid fuel and the secondary solid fuel. 24. The cofiring burner system of claim 23, wherein the mixing element is a diffuser element. 25. The cofiring burner system of claim 23, wherein the mixing element is an impeller. 26. The cofiring burner system of claim 22, wherein the primary solid fuel is pulverized coal. 27. The fuel injector of claim 22, wherein the primary solid fuel is petroleum coke. 28. The cofiring burner system of claim 22, wherein the secondary solid fuel is a biomass fuel. 29. The cofiring burner system of claim 28, wherein the biomass fuel is predryed. 30. The cofiring burner system of claim 22, wherein the secondary solid fuel is petroleum coke. 31. A method of burning a plurality of solid fuels, the method comprising: supplying a primary solid fuel to a burner assembly; supplying a secondary solid fuel to the burner assembly; mixing in a scroll-type or elbow-type fuel injector the primary solid fuel and the secondary solid fuel in the burner assembly until a homogenous mixed fuel is obtained prior to delivering the mixed fuel to a furnace; providing the mixed fuel to a furnace; and combusting the mixed fuel in the furnace. 32. The method of claim 31, wherein the mixing step intimately mixes the primary solid fuel and the secondary solid fuel together. 33. he method of claim 31, wherein the primary solid fuel is pulverized coal. 34. The fuel injector of claim 31, wherein the primary solid fuel is petroleum coke. 35. The method of claim 31, wherein the secondary solid fuel is a biomass fuel. 36. The method of claim 35, wherein the supplying the secondary solid fuel step includes the step of predrying the biomass fuel. 37. The method of claim 36, wherein the step of predrying the biomass fuel occurs before transport to the burner assembly. 38. The method of claim 36, wherein the step of predrying the biomass fuel includes the step of using flue gas recirculation. 39. The method of claim 36, wherein the step of predrying the biomass fuel includes the step of using flue gas recirculation with tempering air. 40. The method of claim 31, wherein the secondary solid fuel is petroleum coke. 41. A fuel injector comprising: a primary inlet port for receiving pulverized coal or petroleum coke as a primary solid fuel; a secondary inlet port for receiving a secondary solid fuel; a mixing chamber within said fuel injector arranged downstream of the primary and secondary inlet ports for mixing the primary solid fuel and the secondary solid fuel to provide a mixed solid fuel; and a nozzle arranged downstream of the mixing chamber at a distal end of the fuel injector for providing the mixed solid fuel to a combustion chamber. 42. A cofiring burner system comprising: a furnace; at least one primary feed pipe for providing a primary solid fuel; at least one secondary feed pipe for providing a secondary solid fuel; and at least one fuel injector abutting the furnace for mixing with a mixing element the primary solid fuel and the secondary solid fuel within the fuel injector and for providing the mixed fuel to the furnace for combustion therein, the mixing element being a diffuser or an impeller.