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A.: Excuse me please, did you say “atmosphere distillation tower”?
B.: No, that is atmospheric distillation tower!
A.: I see. What is this?
B.: This is a tall steel tower with perforated trays. A number of trays are needed
as each fraction has a different boiling range, and
a distillation tower can
separate various fractions using heat and cooling.
A.: I know from the tutorials that heavier hydrocarbons boil at much higher
temperatures than lighter hydrocarbons.
B.: Right you are. So they settle in trays at the bottom of the tower closest to
furnace. As for lighter fractions, they are collected at the top. As each frac-
tion reaches the tray where the temperature is just below its own boiling
point, it condenses, liquefies and is
drawn off the tray by pipes
A.: Oh, my God! What a complicated process it is! I wish I saw it with my own
eyes! What are the final products of the distillation then?
B.: First, gases and light gasoline such as methane, ethane, propane, and bu-
tane. Second, light distillates naphta, and kerosene.
A.: What is naphta used for?
B.: Naphta is used in the production of gasoline and petrochemicals. The third
product is middle distillates (light and heavy gas oils).
Light gas oils are
turned into jet, diesel, and furnace fuels. Heavy gas oils undergo further
chemical processing such as cracking to produce naphta and other prod-
ucts. And the forth product is residual products that are further processed
to produce refinery fuels,
heavy fuel oil, waxes, greases and asphalt.
A.: You said ‘cracking’, didn’t you? What does it mean?
B.: It’s the next step — conversion. By the way, the most widely used conver-
sion methods are cracking and coking!
A.: Why cracking?
B.: This method uses heat and pressure to ‘crack’ heavy hydrocarbon mol-
ecules into lighter ones.
A.: It’s so interesting! I believe this information can be of great help for my
exam!
B.: You are always welcome! Wish you luck at your exam!
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