REDUCTION OF NITROUS-ACID WITH AN AQUEOUS -SOLUTION OF UREA OR SULFAMIC ACID FOR THE TREATMENT OF NITROGEN-OXIDE IN FLUE-GASES

Absorption of nitrogen dioxide from a flue gas in an aqueous solution leads to the formation of nitrous and nitric acids. Nitrous acid is no t stable and decomposes into nitrogen monoxide which is more pollutant than nitrogen dioxide. To avoid that reaction, nitrous acid can be re duced to non-pollutant products through specific reagents. The aim of this work is the reduction of nitrous acid by urea or sulfamic acid in a mechanically stirred closed reactor. Under different operating cond itions (temperatures from 5 to 38 degrees C, pH between 1 and 4, initi al nitrous acid concentration 0.001 or 0.002 kmol m(-3), urea or sulfa mic acid concentration between 0.002 and 1 kmol m-3), our results allo w us to confirm that the kinetics of reaction are of first order with respect to nitrous acid and with respect to the reductor. Values of ra te constants as a function of temperature are given at pH = 1 for urea and at pH = 3 for sulfamic acid. Within the studied range of pH, reac tivity of sulphamic acid is greater than that of urea. (C) 1998 Elsevi er Science S.A. All rights reserved.