Negative effect of industrial waste residue additives (IWRA) on NOx reduction by selective non-catalytic reduction (SNCR) in cement plant: A comparison between copper slag and iron-ore slag

Abstract

The rapid development of cement plants necessitates the involvement of IWRA to improve the production performance of cement, which leads to the suppression of SNCR de-NOx process. However, the specific performance and mechanism of iron-rich waste materials on SNCR remain unclear. This study specifically addresses the effects of iron-ore slag (Fe2O3) and copper slag (Fe3O4) on the SNCR de-NOx process using fixed bed reactor in a simulated precalciner atmosphere ranging from 400 to 1000 °C. The results show that iron-ore slag had a strong inhibitory effect on the SNCR de-NOx process at low-medium temperatures (400 ∼ 800 °C), whereas copper slag could promote the NOx reduction reactions under slightly excessive NH3/NO ratio (NSR) conditions (NSR = 1.3). Both types of slag exhibited a more significant restraining effect on SNCR as ammonia concentration increased. In addition, the influence of trace elements in IWRA is not significant, which proved IWRA has incomparable substitutability and better economy than traditional catalysts. Consequently, these findings offer theoretical guidance for the subsequent implementation of IWRA in actual cement production processes. Additionally, it is advisable to avoid using Fe2O3-containing IWRA and ensure that ammonia injection points are positioned in the high-temperature region (900 ∼ 1000 °C) to achieve higher de-NOx efficiency.