Prevention Method and Mechanism Of Boiler Cold End Corrosion
In boilers, they’re 2 forms of corrosion that can happen. One is that the Hot end Corrosion and another one is that the cold end corrosion.
Because the name indicates the cold finish corrosion can happen within the cold region of the boilers. Usually, the cold region refers to the pre-heater put in simply before the flue gas exit to the stack or induced draft fan.
Mechanism of Cold end corrosion
The sulfur content within the fuel is the major reason for the cold finish corrosion. once the sulfur burns within the boiler, it forms sulfur dioxide. that is comparatively harmless. However, SO2 are any oxidized to form SO3 as a result of the catalytic effects of vanadium pentoxide(V2O5) or iron oxide(Fe2O3) within the fuel itself and.
The presence of even really tiny quantities of SO3 reacts with the steam or water within the flue gas.
Due to this reaction, the SO3 present within the flue gas forms sulphuric acid. once the flue gas temperature falls below the temperature (temperature below that condensation of wet takes place). that results in a severe corrosion downside at the cold finish of the boilers. ie., air pre-heater put in simply before the flue gas exit to the stack or induced draft fans
Prevention methods
The following ways are accustomed to stop the cold corrosion in boilers.
Read: Prevention Methods and Mechanism Of Boiler Hot End Corrosion
Reducing the surplus airflow
Reducing the fuel sulfur content
If high sulfur content fuel usage within the boiler isn’t eliminated then different prevent ways (Fuel additives, {we will|we’ll|we are going to} discuss below) are enforced to cut back the occurrence of cold end corrosion.
Sulfur content plays a significant role once oil is employed as boiler fuel once compare with the coal. within the case of coal-fired boilers, the formation of Sulfur trioxide within the exhaust region (Cold finish of the boiler) can suppress the formation of ash in the coal fireplace boiler.
Reducing wet Content within the Fuel gas
As we tend to see on top of the wetness play an important role within the formation of sulphuric acid. within the coal hearth boiler, the fuel wetness is going to be reduced by varied ways by correct storage and preheating of coal. however, within the case of fuel, it highly tough removes the wetness.
Reducing the steam leak rate
The leak of boiler tubes or excess steam utilized in steam-assisted soot blower might cause adding the wetness content. Also, it’ll alter the temperature of the exhaust flue gas.
Increasing the wetness content within the flue gas cause increasing the temperature of the flue gas. ie., the temperature can rise to a hundred and fifty oC from a hundred and twenty oC. this can result in severe cold finish corrosion.
Fuel Additives
By adding metal base additives within the fuel can cause forming periclase. Thereby it’ll cut back the formation of the sulfur oxide. Also, these additives can manage the catalytic reaction of vanadium pentoxide and iron oxides.
Flue gas Additives
A warm temperature, the Mg reacts with the sulfur to create the Mg compound. Thereby the sulfur oxide formation is going to be reducing. the foremost disadvantage is that the Mg compound can deposit on the preheater tubes and increase the fouling resistance.
The amount of additive to inject within the fuel gas is confirmed by the presence of sulfur trioxide quantity.
Flue gas exhaust temperature
The usual technique used to attenuate the cold finish corrosion by maintaining the flue gas exhaust temperature on top of the dew point. The temperature distinction shall be of 20oC between the flue gas and dew point.
The boiler potency is going to be reducing with the increasing of temperature distinction.
Removing the catalyst
Vanadium pentoxide (V2O5) and ferric oxide (Fe2O3) act because of the catalyst for the SO3 formation reaction. These catalysts that area unit usually found on the surfaces of fueled boilers. catalytic effects area unit influencing by the number of the extent of catalyst exposed to the flue gas.
Therefore, boiler cleanliness, a mirrored image of the number of catalyst gift, affects the number of sulfur trioxide shaped.
Post a Comment