The temperature of the condensation of water vapor in the flue gas of industrial gas steam boiler is called dew point, and the dew point is related to many factors. The water vapor content in the flue gas is high, that is, the water vapor partial pressure is high, and the dew point is high. But the thermodynamic dew point determined by the water vapor partial pressure is lower, for example, the fuel industrial gas steam boiler in general, the partial pressure of the water vapor in the flue gas is about 0.08 to 0.14 absolute atmospheric pressure, and the corresponding thermodynamic dew point is between 41 and 52 DEG C.
The sulfur content in the fuel is high, and the dew point is also high. The sulfur dioxide and the sulfur dioxide are further oxidized into sulfur trioxide when the sulfur in the fuel is combusted. The steam of the sulfuric acid and the steam of the sulfuric acid are generated in the sulfur trioxide and the water vapor in the flue gas, so that the dew point is greatly improved. For example, when the concentration of the sulfuric acid vapor is 10%, the dew point is up to 190.degree. C. The higher the sulfur content in the fuel, the greater the SO2 generated after combustion and the greater the excess air coefficient, the more the SO2 is converted to SO3. Different combustion modes, different fuels, even if the fuel sulfur is the same, the dew point is different. The ash content in the fuel is very low, and the ash in the flue gas adsorbs the sulfuric acid. The ability of steam is very weak. Therefore, even if the sulfur content is the same, the dew point of flue gas when fuel oil is obviously higher than that of coal combustion, so the low temperature corrosion of the tail heating surface of gas steam boiler in oil industry is much more serious than that of coal combustion.
