The oil rejection problem in distillation columns
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When the unit is shut down, how should the naphtha in the pipeline at the top of the fractionator be removed? I read that it’s possible to use water for this purpose; how does everyone do it with water? Is it the tower being filled with water, and then the water overflows from the top of the tower, pushing out the naphtha through the pipeline at the top? Please discuss this, thank you, extra points
There’s no need to go through such complicated procedures to remove oil; a steam blast is sufficient. When it’s time to passivate the distillation tower, water and a passivating agent need to be injected into the oil gas lines at the top of the tower and poured up to the top of the distillation tower itself.
There are two methods for removing oil, and one can be chosen depending on the downtime available. One method involves using water: the reflux pump is activated to pump water from the reflux line into the tower, filling it with water; this water then forces the oil in the top of the tower back into the reflux line. The other method is to use steam to heat the tower, controlling the temperature at the top of the tower; if necessary, air cooling is used to lower the temperature, thereby evaporating the remaining oil in the top of the tower.
What kind of unit’s distillation tower are you asking about? Generally, for light oils, it is necessary to first use water to push out the impurities, and then, after the water has been removed, steam is used for purging