Flue gas temperature
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If the exhaust temperature is to be controlled, what is the normal range for it?
180–250 degrees, a reference value to avoid flue gas corrosion.
Not higher than 180 degrees, to prevent dew point corrosion
The specific value is not specified; instead, it needs to be calculated and measured using the dew point temperature. At the same time, if it is a modified unit, care must be taken to ensure that the temperature of the water entering the drum after heat extraction does not reach the saturation temperature.
First, sulfur trioxide is present in the flue gas； Second, the metal wall temperature of the heat-exposed surface is lower than the acid dew point temperature in the flue gas. There is no uniform standard for this; when sulfur is present in the fuel, it burns to produce SO2. SO2 is further oxidized to SO3, and SO3 combines with water vapor in the flue gases to form sulfuric acid vapor. The higher the sulfur content, the higher the dew point temperature!
The flue gas temperature is related to the furnace temperature, the excess air coefficient, and the opening degree of the flue dampers. When the furnace temperature is high, the natural smoke exhaust temperature rises ； As the excess air coefficient increases, the heat carried away by the exhaust gases increases, leading to a rise in flue gas temperature ； When the flue damper is opened wider, more exhaust gas is emitted from the chimney, which can also increase the exhaust temperature ； When the heat transfer efficiency of the air preheater in the convection chamber decreases, the flue gas temperature also rises. To take into account both the utilization of waste heat from the furnace and the prevention of dew point corrosion, Sinopec requires that the flue gas temperature of the heating furnace be maintained between 130 and 170 degrees.