Serious high temperature corrosion occurred on water wall area of a 600 MW unit boiler.To solve this problem

the effects of the related factors on reducing atmosphere

such as the operation oxygen content and air distribution methods

were investigated.The results show that

the concentration of reducing gas around the boiler water wall area was higher under normal operating mode with 600 MW load condition

of which the volume fraction of CO was about 10 000~30 000μL/L

and that of H_2 S was about 80~130μL/L.Compared with the high-load conditions

the concentration of reducing gas around the boiler water wall area decreased more significantly under low load conditions.With a decrease in air damper opening of over-fire air

the volume fraction of CO in water wall area of the boiler declined obviously.With an increase in the operation oxygen content

the concentration of reducing gas around the boiler water wall area decreased slightly.Compared with other operation modes of the mills

the overall concentration of reducing gas in the boiler wall area is low under conditions with intermediate mill outages.High sulfur content in the coal resulted in an obvious increase in volume fraction of H_2 S in boiler water wall area.It is recommended to burn low-sulfur coal.