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Show • Burner stoichiometry: excess air level for various gas burner firing capacities • Cofire burner front-to-back biasing • Automatic gas burner control for load following Typically, the composite economic benefits for a cofire retrofit will payback the cofire hardware and installation capital costs in 1 to 3 years. Starting in 1995, three coal-fired boilers in Ohio were selected for initial evaluations. These retrofit projects quantified the benefits of cofire for both spreader and mass-feed chain grate coal-fired stoker units with diverse coal types and operational constraints. Specific operational benefits demonstrated included: recovered derate, reduced particulate, extended low load turndown, rapid load following, quick, clean lightoffs, and increased efficiency. O n the basis of these technology validations, G R I extended the program to a broader range of coal-fired applications, and to the wood-fired boiler population. The present work discusses results from the additional coal-fired units retrofitted. TEST PROGRAM Starting in 1996, GRI initiated additional field evaluations of cofire for coal-fired stokers. The purpose of the field programs was to extend and validate the cofire technology for additional boiler designs and cofire benefits. Five sites tested under this effort. Ford Motor Company Cleveland Engine Plant, the Capitol Power Plant in Washington D.C., The Eli Lilly and Company Tippecanoe Laboratories in Lafayette, Indiana, Purdue University W a d e Utility Plant in West Lafayette, Indiana, and the Morton International Plant in Manistee, Michigan, are discussed in this paper. Ford Motor Company Ford Motor Company owns and operates six coal-fired stoker boilers at its Brookpark engine manufacturing facility in Cleveland, Ohio. These boilers have a total steam generation capacity of 500,000 lb/hr with a combined heat input rating of 650 MMBtu/hr. In this project, Ford and East Ohio Gas teamed to retrofit Boiler No. 5, a Riley-Union spreader stoker, with dual Coen CoFyr burners. The boiler has a design capacity of 100,000 lb/hr but has been derated to 70,000 lb/hr to meet opacity and particulate emissions limits. The two primary drivers at Ford for gas cofire were: • Recovery of lost derate caused by excessive particulate emissions at high load • Ability to fire 100 percent gas during summer months when plant demand is low, thereby reducing operating costs normally associated with solid fuel firing. To strike the best balance between these two objectives, the gas burners were sized at 65 MMBtu/hr total heat input. This capacity was sufficient to operate the boiler at 50 percent capacity on gas alone. T o achieve best flame shaping for both low and high gas burner firing capacities, different gas spuds were used for low capacity cofire and high capacity seasonal gas use. Other secondary benefits included clean startups, extended low-load turndown, and increased efficiency. The boiler was retrofit with cofire burners in October 1997 and subjected to a series of performance and environmental tests in December. The testing consisted of continuous monitoring for 0 2 , C O , C 0 2 , and NOx , E P A Method 5 for particulate, Andersen impactor train for particle sizing, grab samples for fuel feed and ash streams, and process data. The burner swirl vanes and gas spuds were changed to achieve broader coverage of the dual objectives cited above, and the tests were repeated in April 1998. 5 |
