System and method for simultaneously removing sulfur trioxide, ammonia gas, and fly ash in flue gas after SCR

Abstract

The invention discloses a system and method for simultaneously removing sulfur trioxide, ammonia gas, and fly ash in flue gas after SCR. A rotary air preheater and an auxiliary flue gas conditioning system are taken as the basis of the system. The system mainly comprises the rotary air preheater, a flue gas online monitoring system, the auxiliary flue gas conditioning system, an electrostatic deduster, a flue gas deep cooler, and a pre-posed air heater. The heat exchange area of the rotary air preheater is reduced, the temperature of the flue gas outlet of the rotary air preheater is raised tothe dew point temperature of ammonium bisulfate or so, ammonia gas and sulfur trioxide in flue gas are used to modify flue gas; at the same time, the auxiliary flue gas conditioning system can adjustand optimize the flue gas conditioning process in real time according to the flue gas information provided by the flue gas online monitoring system. The provided simultaneous removal method can improve the dedusting efficiency of an electric deduster, is capable of removing sulfur trioxide and SCR escaped ammonia gas in flue gas, and solves the problem that a downstream heat-absorbing surface isobstructed and corroded by deposited ash.

Description

technical field [0001] The invention relates to a waste heat utilization and flue gas treatment system for flue gas at the tail of a coal-fired power plant, in particular to a system and method for synergistically removing sulfur trioxide, ammonia and fly ash in flue gas after SCR. Background technique [0002] As we all know, selective catalytic reduction (SCR) flue gas denitrification technology has been adopted by a large number of coal-fired power plants to achieve NO x low emissions. SCR catalyst promotes NO x At the same time of the reduction reaction, part of the SO in the flue gas is inevitably 2 converted to SO 3 . NH escaped from SCR denitrification system 3 Can be compared with the generated SO 3 The reaction produces (NH 4 ) 2 SO 4 and NH 4 HSO 4 . NH 4 HSO 4 It is highly hygroscopic, viscous and corrosive when it is lower than its dew point temperature, and it is very easy to induce ash on the heated area; and NH 4 HSO 4 The condensing temperatur...

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Problems solved by technology

[0005] For the current post-SCR NH 3 and SO 3 The problem of severe fouling, plugging and corrosion of the rotary air preheater and the downstream heat exchanger is caused. Based on the understanding of flue gas conditioning technology, the present invention proposes a method for synergistic removal of sulfur trioxide, ammonia and fly ash in the flue gas after SCR. Gray systems and methods

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