As with distilled, crude oil distillation is also using crude oil each component of therelative volatility of different fractions and separated (see distillation). But crude oil is complex hydrocarbon class mixture, various hydrocarbon (and hydrocarbon and hydrocarbon formed of total boiling real) of boiling point by low to high almost is continuous distribution of, with simple distillation method very difficult separation out pure compounds, General is according to products requirements by boiling point range segmentation into weight different of fractions, so, crude oil distillation Tower and separation pure compounds of distillation column different, its features for:
① Has multiple side outlet, separation accuracy of oil distillation fractions does notrequire high like a distillation of pure compounds, multiple side-port (3~4) can also lead to different fractions.
② Concentration of very short. Crude oil distillation Tower bottom material is very heavy, not suitable for bottom heating. But usually the bottom into superheated steam, the lighter fractions evaporate, generally concentrated trays only 3~4 blocks.
③ The Middle back. Fractions of crude oil with an average boiling points vary widely, causing crude oil distillation Tower steamloads and loads of liquid increasing from bottom to top. Heat recovery for uniform load and high temperatures, Middle back heat (that is, in the central tower for taking liquids, heat cool heat recovery and then sent back to the Tower). 2~3 usually a middle return.