COMBINED AIR PREHEATER SUITABLE FOR POST-SCR DENITRATION, AND ANTI-CORROSION AND ANTI-BLOCKING METHOD

摘要

A combined air preheater suitable for post-SCR denitration. The air preheater comprises a flue (1) and an air duct (2) which are positioned downstream a denitration device, and also comprises a secondary air section (3), a primary air section (4), an ammonium bisulfate condensation resistant section (5) and an ammonium bisulfate solidifying section (6) which are sequentially arranged along the flue gas flowing direction. The primary air section (4), the ammonium bisulfate condensation resistant section (5) and the ammonium bisulfate solidifying section (6) are phase change heat exchangers. The phase change heat exchanger comprises a heat absorbing section (7) positioned in the flue, a heat releasing section (8) positioned in the air duct, and an ascending pipe (9) and a descending pipe (10) which are used for connecting the heat absorbing section and the heat releasing section, the heat releasing section (8) is higher than the heat absorbing section (7), and a circulating medium is arranged in the phase change heat exchanger. The wall surface temperature of the ammonium bisulfate condensation resistant section (5) is higher than the dew point temperature of ammonium bisulfate, and the wall surface temperature of the ammonium bisulfate solidifying section (6) is lower than the freezing point temperature of ammonium bisulfate. The combined air preheater eliminates the phenomenon that liquid ammonium bisulfate blocks the heating surface of the air preheater due to dust, and also effectively prevents the liquid ammonium bisulfate from corroding the air preheater.