Intensification of NO x Conversion over Activated Coke by Ozone Oxidation for Sintering Flue Gas at Low Temperatures.

Abstract

Denitration (De-NOx) over activated cokes (ACs) for sintering flue gas needs intensification. Gaseous reactions in a gas mixture containing NO, NO2, and NH3, with the effect of O2 concentration and moisture, were taken into consideration in the study of NOx conversion over ACs. Experimental studies on NOx conversion with and without NH3 over ACs were conducted using a fixed-bed reactor at 100 °C. The results demonstrated that moisture significantly affected NOx removal over ACs, especially the NO2 conversion. Under dry conditions, a disproportionation reaction of NO2 over ACs dominated NOx conversion with no NH3, whereas apparent fast selective catalytic reduction (SCR) over the ACs was observed in the presence of NH3. Regardless of the presence of absence of NH3 in wet mixtures, NO2 adsorption on ACs via the disproportionation route dominated the NOx conversion. Increasing the NO2/NO ratio in the simulated flue gas enhanced the NOx conversion rate over ACs. −C(ONO2) deposition on ACs generated by the disproportionation route inhibited NOx conversion with time. O3 oxidation was found to be efficient in increasing the NO2/NO ratio and intensifying the NOx conversion compared with commercially direct NH3-SCR over ACs. Increasing the temperature and decreasing the gas hourly space velocity can promote NOx conversion over ACs after O3 oxidation. NO oxidized with O3 coupled with NH3 spray and continuous regeneration of ACs is a potential method for removing NOx from sintering flue gas.