OCR Text |
Show 1- I ~.~ atmospheric lightning which promotes the reaction of atmospheric oxygen and nitrogen. The temperature of a column of air exposed to lightning is a function of energy deposition of the lightning. For a typical energy deposition of about 105 Jim, the column of air immediately surrounding the charge is heated to temperature on the order of 30,000K. At temperature above 2,300K, NO is in thermodynamic equilibrium with N2 and 02 _~ As the temperature of the heated air drops below 2,000K, NO "freezes" as a stable compound (Levine, 1984). It has been found from field flux measurements and laboratory experiments that soil microorganisms may also produce appreciable amounts of NO. Nitrification is an aerobic process in which ammonium is oxidized to nitrite and nitrate. NO and N20 are direct or indirect intermediates of this pathway (Levine, 1984). NOx diffusion from the stratosphere is a third an important source of tropospheric NOx . Various emission standards·, limits and regulations have been promulgated to control NOx emission. In the US, the primary ambient standard for nitrogen dioxide is 10oug/m3 ; taken as an annual arithmetic mean. Table 1 compares the new source perforrn~ nce for NO~ control standards (NSPS) for a number of industriallzed countrles. Table 1. Emission standards for New Power Plants (taken as g of N02 ) Fuel (g MJ-1) State power (MW) solid liquid gas S wi tzeriand > 300 0.07 0.04 0.03 50-300 . 0.14 0.07 0.05 1-50 0.18 0.07 0.05 Austria > 300 0.05 0.03 0.02 -Draft 150-300 0.11 0.06 0.04 , 50-150 0.11 0.08 0.05 Netherlands > 300 0.14 0.08 0.05 50-300 0.18 0.08 0.05 FRG > 300 0.07 0.04 0.03 50-300 0.14 0.08 0.05 1-50 0.18 0.13 0.05 Japan > 550 0.14 0.07 0.03 400-550 0.18 0.07 0.03 30-400 0.18 0.09 0.06 5-30 0.25 0.09 0.07 < 5 0.25 0.10 0.08 USA > ;3 0.28 0.14 0.09 29-73 0.32 0.14 0.05 2 |