NOx removal in the selective non-catalytic reduction (SNCR) process and combined NOx and PCDD/Fs control

NOx removal from flue gases by selective non-catalytic reduction (SNCR) was investigated with special attention paid to combined dioxin destruction in waste incineration plants. For the SNCR technology, ammonia (NH₃) and urea-based reductants are widely adopted, and the important factors affecting De-NOx efficiency associated with SNCR were investigated here, including the effective temperature range, normalized stoichiometric ratio (NSR) of NH₃ (or urea)/NOx. However, NH₃ slip and N₂O emissions are the two common problems related with the SNCR process and operating conditions should be delicately designed for their control. With respect to combined dioxin control in De-NOx process, the technology is mainly related to selective catalytic reduction (SCR) since the effective temperature range for SNCR is away from the dioxin formation temperature zone. But there was also investigation showing that the SNCR process based on hydrazine hydrate exhibited some dioxin reduction. In order to control PCDD/Fs effectively, and to prevent NH₃ slip and N₂O emission in the SNCR process, it is suggested that the reagent corresponding to lower SNCR effective temperature range should be investigated.