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Show THE EFFECT OF COMBUSTION MODIFICATIONS ON SCR PERFORMANCE L. J. Muzio, R. L. Hack Fossil Energy Research Corp. Laguna Hills, CA 92653 D. P. Teixeira Pacific Gas and Electric Company San Ramon, CA 94583 ABSTRACT Extensive use of combustion modifications for NOx control can lead to higher NO/NOx ratios in the flue gas, particularly for natural gas-fired utility boilers. This in turn can impact a selective catalytic NOx reduction process located downstream of the boiler. A bench-scale study was conducted to determine the effect of varying NO/NOx ratios on the performance of a commercial vanadialtitania SCR catalyst. The test results show that the catalyst activity is increased with the presence of N02, the stoichiometric NH3 requirement varies with SeR operating conditions, and whether NO or N02 is preferentially removed by the catalyst depends on the NO/NOx ratio. INTRODUCTION In recent years, NOx emission regulations have become more stringent for natural gasand oil-fired utility boilers. This has required utilities to incorporate selective catalytic NOx reduction (SCR) as part of their compliance strategies. SCR involves the reaction between ammonia (NH3) and NOx over a catalyst located between the economizer exit and inlet to the air preheater (Le., where the temperature is in the range of 650°F to 750°F). While SCR has the capability of achieving high levels of NOx removal, SCR is generally used in conjunction with combustion modifications for NOx reduction. Presented at Pacific Rim International conference on Environmental Control of Combustion Processes. AFRC/JFRC of the IFRC, Maui, Hawaii, October 16 - 20, 1994 |