The report describes the final of three phases of a program to determine the optimum methods of applying both flue gas recirculation (FGR) and staged combustion (SC) to control nitrogen oxides (NOx) emissions from residual oil-fired package boilers. Experimental investigations were carried out in a laboratory firetube boiler simulator, and an application program was conducted on two boilers operating in the field. The ultimate goal of the program was to determine if package boilers can operate in the field after modification to control NOx emissions without encountering practical problems. A 12 million Btu/hr firetube boiler and a 25 million Btu/hr heat output watertube boiler were modified to extract cooled combustion products from the stack and add them to the combustion air in the windbox. The effectiveness of FGR as a method of controlling NOx emissions was found to be dependent upon boiler type. It was most effective in the firetube boiler: approximately 30% reduction in emissions was obtained with 40% recirculation. NOx reductions achieved by SC were greater in the field tests than in the laboratory investigation. Reductions of 45% were achieved without undue smoke emissions when 70% of the stoichiometric air requirements were applied to the burner.

"January 1977." Prepared under Contract 68-02-0222, ROAP 21ADG-043, program element 1ABO14 for American Petroleum Institute and U.S. Environmental Protection Agency. Includes bibliographical references. "EPA/600-2-77-025." "EPA Project Officer: G. Blair Martin"--Beneath title.