Effects of Hybrid Reburning System with SNCR and Air Staging on NOx Reduction and Thermal Characteristics in Oxygen-Enhanced Combustion

Abstract

The reburning process has been demonstrated to be a very effective and simple technique for reducing NOx emission and has been successfully applied to many industrial fields. Likewise, the air staging process is one of the most effective techniques for control of NOx emission. Nowadays, selective non-catalytic reduction (SNCR) method has been suggested as the advanced process for NOx reduction. The main goal of this study is to examine the effects of hybrid reburning system with SNCR and air staging on NOx reduction. Experimental study has been done to examine the formation characteristics of NOx in a lab scale combustor (15 kW) with various oxygen-enhanced combustion conditions. This study reports four experimental cases. Experimental case 1 was performed regarding the reburning process. Reburn fuel fraction in the reburning zone and the amount of additional air in the burnout zone have been studied for NOx reduction. Air staging and hybrid reburning with air staging effects were considered in experimental case 2. The effects of air staging on the gas temperature distribution and heat flux rate were studied. For case 3, SNCR process was considered. The effects of various NH3 fraction values and the amount of main air on NOx reduction and CO emission were considered when oxygen enhanced combustion was used. Finally, hybrid reburning system with SNCR and air staging were studied for case 4. Based on the effectiveness of each De-NOx process, the advantage of hybrid reburning system with SNCR and air staging was found and discussed.