Diesel hydrogenation
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The top temperature of the fractionation tower is controlled at around 145, while the dry point of the naphtha is controlled at 170. With such a large temperature difference, how can the naphtha temperature reach 170?
The temperature at the top of the tower is lower than that at the bottom, and there is a reboiler at the bottom
The function of a distillation tower is to separate substances, and the principle behind this separation relies on the different volatilities of various components at different temperatures. For example, the boiling point of water is 100 degrees, but at temperatures below 100 degrees, different vapor pressures are still present to maintain a certain gas-liquid equilibrium.
There is no one-to-one relationship between the tower top temperature and the distillation range
The distillation tower is under pressure, but the Enneberg distillation method used to determine the boiling range is performed at atmospheric pressure!
Since the naphtha partial pressure is lower than standard atmospheric pressure, laboratory tests are conducted at atmospheric pressure
A fractional distillation tower separates unbalanced light and heavy components through multiple contacts; under ideal conditions the dry point is 145, but the separation is not perfect, and it’s inevitable that some heavy components will end up in the product