Combined air preheater suitable for SCR (Selective Catalytic Reduction) post-denitration, and anti-corrosion and anti-blocking method

Abstract

The invention provides a combined air preheater suitable for SCR (Selective Catalytic Reduction) post-denitration, which comprises a flue and an air duct which are arranged downstream a denitration device, and also comprises a secondary air section, a primary air section, an ammonium bisulfate condensation resistant section and an ammonium bisulfate curing section which are sequentially arranged along the flue gas flowing direction, wherein the primary air section, the ammonium bisulfate condensation resistant section and the ammonium bisulfate curing section are phase change heat exchangers, and the phase change heat exchanger comprises a heat absorbing section positioned in the flue, a heat releasing section positioned in the air duct, and a riser and a downcomer which are used for connecting the heat absorbing section and the heat releasing section; the heat releasing section is higher than the heat absorbing section, and a circulating medium is arranged in the phase change heat exchanger; the wall surface temperature of the ammonium bisulfate condensation resistant section is higher than the dew-point temperature of ammonium bisulfate, and the wall surface temperature of the ammonium bisulfate curing section is lower than the freezing point temperature of ammonium bisulfate. The combined air preheater puts an end to 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.

Description

technical field [0001] The invention relates to an air preheater, in particular to a combined air preheater suitable for SCR denitration and a method for preventing corrosion and blocking. Background technique [0002] NO x It is one of the main pollutants causing acid rain and photochemical smog. Currently, with ammonia (NH 3 ) as the reducing agent for the selective catalytic reduction (SCR) flue gas denitration technology is the industrial removal of NO x effective method. The so-called SCR denitration technology is to set a denitration device in the inlet flue behind the boiler economizer and above the rotary air preheater, and use the flue gas temperature of 300°C to 400°C after the boiler economizer to inject and dilute it under the action of a catalyst. The ammonia gas can chemically react with the nitrogen oxides in the original flue gas to generate pollution-free nitrogen and water vapor, thereby reducing NO x emission. [0003] Due to the limitation of denitr...

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Problems solved by technology

[0007] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a combined air preheater suitable for SCR denitrification, to solve the problem of liquid ammonium bisulfate corrosion and blockage of the air preheater caused by denitrification in the prior art. Defects on the heating surface of the heater

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