Experimental and modeling study of the effect of CO and H 2 on the urea DeNO x process in a 150 kW laboratory reactor

Abstract

An experimental and modeling investigation has been performed to study the effect of process additives, H 2 and CO on NO x removal from flue gases by a selective non-catalytic reduction process using urea as a reducing agent. Experiments were performed with a flow reactor in which flue gas was generated by the combustion of propane in air at 3% excess oxygen and the desired levels of initial NO x (500 ppm) were achieved by doping the flame with ammonia. Experiments were performed throughout the temperature range of interest, i.e. from 850 to 1200 °C for investigation of the effects of the process additives on the performance of aqueous urea DeNO x . Subsequently, computational kinetic modeling with SENKIN code was performed to analyze the performance of urea providing a direct comparison of modeling prediction with experimental measurements. With CO addition, a downwards shift of 215 °C in the peak reduction temperature from 1125 to 910 °C was observed during the experimentation while the kinetic modeling suggests it to be 150 °C, i.e. from 1020 to 870 °C. The addition of H 2 impairs the peak NO x reduction but suggests a low temperature application of the process. A downward shift of 250 °C in the peak reduction temperature, from 1020 to 770 °C, was observed during kinetic modeling studies. The kinetic modeling shows a good qualitative agreement with the experimental observations and reveals additional information about the process.