According to the different corrosion parts and environments, the corrosion of boiler water wall tubes includes two categories: water vapor side corrosion and fire side corrosion. The preventive measures are as follows:
① Change the operating conditions to ensure the furnace temperature. Raising the furnace temperature can not only prevent the wall temperature of the heating surface from falling to the dew point temperature of the flue gas, but also effectively prevent the formation of sulfur trioxide. Therefore, the number of start and stop of the boiler should be minimized to keep the boiler in continuous operation. It is recommended that the high-pressure heater should be put into operation as long as possible to ensure the safe and stable operation of the boiler under economic conditions.
②Strengthen the control of fuel. The method of sulfur removal before and during combustion can be adopted to reduce the sulfur content of the fuel; at the same time, the appropriate fineness of pulverized coal can be controlled to evenly distribute the pulverized coal concentration between the burners;
The quality of the coal used should be tested and analyzed, and the use of fuels with high sulfur content should be avoided as much as possible, and if necessary, chemical additives to prevent the formation of sulfur trioxide in the flue gas can be added, such as dolomite powder, lime powder, etc., which can effectively prevent or reduce the formation of sulfur trioxide.
③ Strengthen the control of water supply quality. Appropriately increase the water flow velocity in the water-cooled wall tube in the high temperature corrosion area, reduce the tube wall temperature, strictly control the quality of the feed water, and avoid the heat transfer caused by the scaling in the water-cooled wall tube, which will lead to an increase in the temperature of the water-cooled wall tube wall; excessive mixing of water with fuel should be avoided; water leakage should be avoided on the furnace wall, especially the use of a large amount of tap water to flush the furnace roof to keep the furnace wall dry.
④ Improve the corrosion resistance of metals. The metal (nickel, aluminum) thermal spraying process can be used outside the tube for surface protection and reduce corrosion rate.
⑤ Strengthen the combustion adjustment and rationally distribute the air to achieve the two purposes of reducing the reducing atmosphere near the water wall tube and avoiding the direct flushing of the water-cooled wall by the flue gas.
⑥ Strengthen sewage management, conduct strict assessment, and ensure the quality of boiler feed water is qualified. It is recommended to do an aerodynamic field test every year.
