Surfactants as additives for NO_x reduction during SNCR process with urea solution as reducing agent

摘要

NO_x reduction from gas stream by selective non-catalytic reduction (SNCR) using urea as a reducing agent was performed in this study. A Pilot-scale experimental system was designed and constructed to evaluate the NO_x reduction efficiency and temperature window of the process. Particularly, different types of additives were added during SNCR process to improve NO_x reduction efficiency and enlarge temperature window. The addition of additives was based on organic compounds like alcoholic group (CH_3OH, C_2H_5OH and C3H7OH) and metallic compounds like alkali metals (NaOH, KOH and LiOH). Some newly introduced additives, such as surfactants and different blends of alkali metal NaOH (1%) with organic group or surfactants were also added to assess the effect of these mixed additives on NO_x reduction efficiency and reaction temperature window during SNCR process. Main focus was laid on surfactants as an additive because of their cost effectiveness and availability. Basically, surfactants have both organic and metallic parts which provide -OH free radicals from both ends (organic and metallic) to enhance the reaction mechanism and improve the NO_x reduction at low temperature. Different types of surfactants (anionic, cationic, amphitricha, long chain, short chain and with different functional groups attached to chains) were tested as an additive during SNCR process. Anionic surfactants (SPES, APS, LAS and SPS) gave maximum efficiency for NO_x reduction and provided maximum range for the temperature window.