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Show INTRODUCTION BURNER IMPROVEMENTS AND FLAME QUALITY STUDIES ON A 650 MW SUPERCRITICAL PULVERIZED COAL BOILER The combustion studies reported in this paper are a result of testing performed with several different burner modifications in a 650 MW wall-fired pulverized coal boiler. Two of Cleveland Electric Illuminating Company's 650 MW Babcock & Wilcox supercritical once-through boilers were retrofitted with new burners and tested extensively. Also, testing and video taping of flame patterns of initial prototype designs was done in a 50 MW wall-fired boiler. The conclusions drawn from this testing, although somewhat subjective, should be of interest to anyone attempting to improve combustion in a similar boiler. The testing program began in early 1986 following installation of new burner air registers in CEI's Avon 9 boiler and conversion of the furnace from pressurized to balanced draft operation. Following these changes, the unit suffered severe combustion problems which prompted an extensive testing program as attempts were made to identify possible causes and fixes. Since then, additional testing has transpired as new problems have arisen and new burner innovations were developed and tested. The most recent work has encumpassed testing on Eastlake 5, an identical sister unit to Avon 9, before and after retrofitting with the new burner. Data from the various tests on all three boilers has been used to assess the impact of burner design features on furnace temperatures, slagging patterns, CO levels in the combustion zone and flame patterns. History of Combustion Problems Both Avon 9 and Eastlake 5 are 650 MW units having identical B&W (UP type) supercritical once-through boilers. Each boiler has six MPS type pulverizers with 48 burners opposed on the front and rear walls. These units burn high sulfur Ohio coal from several mines as well as increasing amounts of spot coal purchases. Typical coal and ash analysis are shown in Table No.1. Note the relatively small differences in ash, Btu content and ash fusion temperatures that differentiate the better performing coals from the marginal. Figure No. 1 shows the Avon 9 boiler. Avon 9 went into service in 1970 and Eastlake 5 in 1972. Both boilers were originally designed as pressurized furnaces with gas recirculation at the bottom and through upper gas tempering ports for temperature control. The gas recirculation was later eliminated. Industry experience has borne out that B&W boilers of this type and vintage were severely undersized in furnace volume and burner zone area, particularly for lower fusion coals. Consequently, from early hist9ry, these B&W uni~s as well as others in this country, suffered from combustion problems, furnace slagging being the worst. CEI's experience has been that only higher quality coal, as indicated in the typical analysis, can be burned satisfactorily in these units. |