Transcription of Calculating NOx Levels - Bloom Eng
1 Measured) O % - ( )- ( measured O % at ppm = O 3% at ppm222 Equation 1 Emission Levels are also expressed as pounds of NOX per million Btu or per hour. Common practice is to use theweight of NO2 for Calculating the NOX Levels with the following two equations:Equation 2 HHV X )O % measured - ( X 379 PFRS X NO ppm measured X 46 X = Btu /millionNO million X Btu /millionNO lb. = the United States, the fuel's higher heating value (HHV) is used in the calculations. Lower heating values (LHV) areused in many other countries. Average natural gas (1050 Btu/ SCF, HHV) at stoichiometric ratio produces dry SCF products of combustion per SCF of fuel. This volume varies with actual gas NOX emission data are expressed in ppm corrected to some standard oxygen level it DOES NOT necessarilymean that the fuel was actually burned with this amount of excess oxygen.
2 The correction is only a mathematicalcalculation. For example, the Japanese correct their NOX data to 11 percent O2 dry. Obviously their process furnacesare not operating at over 80 percent excess air which is equivalent to 11 percent excess that there may be (and probably is) a difference between actual field conditions and ppm data correctedto a standard condition is important. As excess air Levels increase from stoichiometric conditions, NOX increasesrapidly. To understand a burner's NOX characteristics, it is necessary to know what excess air level was actually usedfor combustion as well as the ppm level and the corrected oxygen basis. Using data expressed in pounds of NO2 permillion Btu (HHV) eliminates much of the confusion.
3 WherePFRS = SCF products of combustion per SCF of fuel at stoichiometric ratiolb. NO2/ lb. Mole = 46 SCF NO2/ lb. Mole = 379 HHV = higher heating value of fuel in Btu/ SCF Note:Either wet or dry basis can be used but PFRS and measured % O2 must be equation is for combustion without exhaust gas 3 CNL-G-001-9717115460 Horning RoadPittsburgh, PA 15236 Phone 412-653-3500 Fax 412-653-2253e-mail: Bloom Engineering Company, flue gas analyzers measure NOX in parts per million (ppm) by volume on a dry basis. The measurements are often corrected to some standard such as 3% oxygen using Equation NOx Levels
