NO{sub x} controls for Group 2 boilers

The Clean Air Act Amendments of 1990 require that NO{sub x} emission limits be established for two categories of coal-fired utility boilers. These categories are designated as Groups 1 and 2. Group 1 consists of dry bottom wall-fired and tangentially-fired boilers. Group 2 comprises all other utility boiler types including cell burner, arch-fired, wet bottom and cyclone-fired boilers. Wall-fired boilers equipped with cell burners are an important segment of the Group 2 boiler population. Low-NO{sub x} CCV cell burners have been successfully retrofitted on a 600 MW coal-fired cell burner boiler. NO{sub x} reductions of 50% have been demonstrated using this technology. This performance was achieved without increasing unburned carbon in the boiler fly ash and without boiler pressure part modifications. In addition to cell burner boilers, NO{sub x} control strategies also exist for other Group 2 boilers including the Riley dry bottom TURBO{reg_sign} furnace, wet bottom and cyclone-fired boilers. Over the past decade or more, combustion NO{sub x} controls have been successfully applied to several types of slag-tap utility boilers in Europe without adversely affecting operational performance. NO{sub x} reductions of 30 to 60% have been achieved on these units through a combination of combustion modification techniques.