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Show SUMMARY AND CONCLUSIONS The placement and design of a gas cofiring burner over a coal spreader stoker boiler has been evaluated with CFD analysis in this study. Cofiring burner penetration and furnace mixing was predicted with CFD for both high and low boiler loads at maximum and minimum cofiring burner firing rates, respectively. The cofiring burner separation distance was investigated with separations of 4, 6, and 8 ft. The CFD results indicated that the 8 ft. burner separation distance provided (1) superior furnace mixing, (2) maximum furnace penetration, and (3) no indication of flame impingement. The following conclusions can be drawn: • CFD has proven a valuable tool in the prediction of the flame shapes and flow patterns within the furnace and to identify potential problem areas of operation. • Greatest mixing within the furnace occurs at the highest cofiring percentage levels. • Minimum gas cofiring percentage levels provide minimal furnace mixing and cofiring benefits. • The gas cofiring burner design offers stable operation over a wide operating range and burner stoichiometric ratios. • The gas cofiring burner provides simpler boiler start-up with flexible wann-up and nearl y smokeless light off of coal. • Reduced gas cofiring burner spuds offer enhanced mixing at low gas cofiring percentage levels. ACKNOWLEDGMENTS The author wishes to acknowledge the funding of this study from the Gas Research Institute, GRI contract number 5094-230-2885 with Isaac Chan acting as Program Monitor. Also gratefully acknowledged are the guidance and suggestions received by the author from Howard Mason Jennifer Pont, and Carlo Castaldini of Acurex Environmental, Corporation and Ward "Bud" Kinney of East Ohio Gas. Assistance from Coen Company, Inc. personnel include Jon Backlund, Tim Webster, and Steve Londerville. The author also wishes to thank Julie Webster for her efforts in the preparation of this manuscript. Finally, grateful acknowledgment to Dave Borland and the boiler operators of the City of Dover, Ohio for their support during the project. 8 |