The Reduction of Noxious Emissions Using Urea Based on Selective Non-Catalytic Reduction in Small Scale Bio Fuel Combustion System

Abstract

Selective Non-Catalytic Reduction (SNCR) of oxides of nitrogen (NOx) was studied experimentally by injecting different concentrations of aqueous urea solution in a pilot-scale Bio-fuel 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 small-scale combustion systems where the operating temperatures are usually in the range of about 973 to 1323 K and NO x emission level remains below 100 ppm. NO x reductions were studied with the variation of different parameters such as injection temperature, residence time, Normalized Stoichiometric Ratio (NSR) of the reagent, carrier gas pressure, etc. A significant amount of NO x reduction was achieved which was not pronounced by the previous researchers with urea SNCR for this low ppm of NO x . With 5% plain urea solution, at an NSR of 4 as much as 54% reduction was achieved at 1128 K, whilst in the additive case the NO x reduction was improved to as much as 69% at 1093 K.

The Used of Aqueous Urea Solution in Reduction of Noxious Emissions in Bio Fuel Combustion System Using Selective Non-Catalytic Reduction

“…Some additives are applied to widen the reaction temperature range. If urea is used, the temperature window ranges from 1199 to 1310 K. However, with the addition of additives, the effective temperature range expands to 1088 to 1421 K. In general, NO x reductions are lower and chemical consumption is higher as compared to Selective Catalytic Reduction (SCR) (Ishak and Jaafar, 2011). Typical reagent/inlet NO x stoichiometries are 2:1.…”