Principle of Combined SNCR+SCR Denitrification Process in Cracking Furnaces

     Principle of SNCR+SCR Combined Denitrification Process for Cracking Furnaces

     Cracking furnaces are widely used in industries such as petroleum and chemicals. For example, waste tire cracking furnaces generate a large amount of flue gas during operation, which contains NOx that urgently requires treatment by denitrification equipment. Which type of denitrification equipment is best for cracking furnaces? We can only choose from SCR, SNCR, SNCR+SCR, and PNCR denitrification processes. Here, we introduce the principle of the SNCR+SCR combined denitrification process for a cracking furnace at a chemical plant in Hefei, Anhui:

    Principle of SNCR+SCR Combined Denitrification Process for Cracking Furnaces

     The SNCR+SCR combined denitrification process for cracking furnaces integrates SCR denitrification (high efficiency) with SNCR denitrification (low investment cost). Typically, the SNCR+SCR hybrid process system is divided into two reaction zones:

     1. First, the denitrification reducing agent is injected into the first reaction zone (with the boiler furnace acting as the reactor) through the SNCR denitrification injection system installed on the boiler wall (SNCR denitrification). Under high temperatures of 850–1100°C during combustion in the furnace, the reducing agent reacts with NOx in the flue gas through a reduction reaction, converting NOx into N2 and H2O, thereby achieving the first step of denitrification.

     2. The unreacted reducing agent from the first step, after thorough mixing with the flue gas, enters the second reaction zone of the combined process system, which is the SCR reactor. In this denitrification device, the ammonia escaping from the SNCR reactor selectively reacts with the unreduced NOx in the flue gas under the action of a catalyst, producing N2 and H2O, thereby achieving further and deeper denitrification.