1. The main factors affecting low temperature corrosion of air preheater are formation of sulfur trioxide in flue gas, the flue gas dew point, the concentration of sulfuric acid and condensation acid content and the metal temperature of heating surface. 

2. The measures for reducing and preventing low temperature corrosion in air preheater are: Improve the metal wall surface temperature of air preheater ; Adopt hot- pipe type air preheater Use corrosion- resistant materials; Apply low oxygen combustion mode; Adopt the additives that can reduce lower dew point or inhibit corrosion; Desulfurize the fuel. 

What measures to be taken for preventing low temperature corrosion to air preheater:

1.Adopt low oxygen combustion. SO3 in the flue gas can be reduced in great quantities, flue gas dew point and corrosion rate are reduced, but incomplete chemical combustion has increased, the fume exhaust loss is reduced, the boiler efficiency is increased slightly. 

2. Control the hearth combustion temperature level and reduce the generation of SO3. 

3. Purge the ash on a regular basis to remove dust and to prevent the corrosion at low temperature. 

4. Flush on a regular basis. If ash accumulates at cold section of air preheater, alkaline water may be used for flushing the surface to remove the ash. After flushing, the original fume exhaust temperature generally can be restored, the corrosion is reduced. 

5. Avoid and reduce the air leakage from heating surface at the rear part. Because of air leakage, temperature of heating surface is reduced, thus accelerating corrosion. Especially when the air leaks from air preheater, the temperature of the air leakage position will be reduced greatly, causing serious corrosion at low temperature.