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Show -2- BACKGROUND Under an agreement with the Massachusetts Department of Environmental Protection (DEP), New England Power (NEP) is required to reduce NOx emissions from the coalfired units at their Salem Harbor Generating Station. The agreement limits NOx emissions to 0.33 Ib/MMBtu (about 240 ppmc) from these units once all of the NOx control equipment is installed. This represents a nominal 70 percent reduction from the baseline NOx emissions levels of approximately 1.0 Ib/MMBtu (700 ppmc). To achieve this NOx emissions goal, NEP has chosen to retrofit these units with ureabased Selective Non-Catalytic Reduction (SNCR) systems supplied by Nalco Fuel Tech. Subsequent to the SNCR retrofit, Unit 3 has also been retrofit with 10w-NOx burners (LNB) and an overfire air (OFA) system supplied by Riley Stoker. DESCRIPTION Salem Harbor Unit 3 is a front wall-fired, B&W boiler which is currently rated at 155 MW 9r9ss for normal claim capacity operation. Figure 1 presents both side and front views of the boiler. Its maximum steam flow is 1,000,000 IbS/hour. The unit has a design steam pressure of 2225 psig at 1 000°F/1 OOooF superheat and reheat temperatures. Unit 3 has 16 burners arranged in four elevations of four burners each. The furnace has a single division wall, placing each burner adjacent to a waterwall. Both the vertical and horizontal burner spacing is uneven. Spacing between the upper two and lower two burner elevations (Le., 6.3 ft.) is less than the spacing between the two center burner elevations (Le., 10.4 ft.). Similarly, the spacing between the outermost burner columns is smaller than that between the two center burner columns. The unit is a balanced draft design, utilizing dual 10 and FO fans. The Riley Model 90 Controlled Combustion Venturi (CCV) burners retrofit to Salem Harbor Unit 3 are designed to fire either pulverized coal or No.6 fuel oil. When firing pulverized coal, NOx emissions are reduced by delaying the fuel/air mixing. This delay is achieved through the use of a venturi coal nozzle and a low swirl spreader design. |