Issues regarding the material selection for distillation column tubes
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For the reboiler tubes in the distillation towers of gasoline (coal, firewood) hydrogenation units and continuous reforming units, grade 20 steel is used; the furnace temperature is 600°C. However, according to the temperature limits for commonly used furnace tube metals, the maximum operating temperature for carbon steel is 450°C, while the ultimate design temperature limit is 540°C – both of which are lower than the furnace temperature of 600°C. Then why can grade 20 steel still be chosen for such designs?
What is the wall temperature? If the temperature used in the heat transfer calculation for the tube wall is not high, 20 is sufficient. Furnaces at 1000℃ use furnace tubes with a diameter of 20
Since cold material flows inside the pipe, the wall temperature of the pipe cannot reach the furnace temperature. If the furnace tube burns out due to dry burning, it will get punctured.