Application of selective non-catalytic reduction of NO_x in small-scale combustion systems

摘要

The selective non-catalytic reduction of NO_x has been studied experimentally employing commercial grade urea in a pilot-scale diesel-fired tunnel furnace at 3-4% excess oxygen level and with low ppm of baseline NO_x ranging from 65 to 75 ppm within the investigated temperature range. The furnace simulated the thermal behavior of small-scale combustion systems such as small capacity boilers, water heaters, oil heaters, etc., where the operating temperatures remain within the range of 950-1300K. NO_x reductions were studied with the variation of injection temperature, residence time, normalized stoichiometric ratio (NSR) of the reagent, etc. With 5% urea solution, at an NSR of 4, as much as 54% reduction was achieved at 1128K. The result is quite significant, especially for the investigated level of baseline NO_x. The ammonia slip measurements showed that the slip was below 16 ppm at NSR of 4 and optimum temperature of NO_x reduction. Finally, the investigations have demonstrated that selective non-catalytic reduction process is quite applicable to the small-scale combustion applications.