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Show COAL OH WASTE SPREAOERS COAL OR WASTE SPREADERS Figure 1. Cofire System. The cofire system features dual, opposed, offset, high-pressure drop burners with an integral forced-draft fan for each burner. The 10-inch pressure drop is essential to give 5 major benefits: • Enhanced mixing in the firebox via deep flame penetration into the solid fuel combustion gases and due to the torroidal mixing pattern • Strong swirl in each individual flame which gives local mixing and entrainment of combustion products into the gas flames • Small burner throat diameter giving easy access, placement flexibility and minimal interference with watertubes • Large burner load turndown, typically 10:1, to permit performance at low cofire or as a standalone start-up or standby burner • Wide stoichiometry range for operation at high excess air levels, effectively acting as overfire air, or at fuel rich conditions for N O x control These features give an independently controlled gas combustion zone, but one which intensely interacts with the solid-fuel flames. The cofire burner concept was to use a standardized burner hardware configuration, to reduce site specific custom engineering and fabrication, but to retain sufficient site specific flexibility to allow coverage of a variety of operating modes. The burner parameters, which can be specified to meet site specific performance goals, are: • Burner capacity • Burner throat diameter and geometry • Burner placement: separation and height above grate • Swirl • Gas injector design These hardware parameters are selected based on the ensemble of benefits sought from cofiring, as described in the next section. 3 |