7. Refinery Gas Plants

Question 1

■ Lean Oil?
■ Rectified Absorbers?
■ Fat Oil?

■ Sponge Oil?
■ Rich oil?
■ Errant Lean Oil?

Answer 1

■ Lean Oil - a naphta range liquid usually heptane C7H16 or Octane C8H18.

■ Rectified Absorbers & ■ Fat Oil:

▪ Rectified Absorbers - Depressurized Propane (C3H8), Butane (C4H10) & little bit of Ethane (C2H6) and Methane (CH4) goes to rectified absorber (column) with special counterflow to be absorbed by Naphta range liquid (Heptane C7H16 or Octane C8H18).

▪ Fat Oil - The naphtha now laden with the propane and butane is called fat oil.

■ Sponge Oil -
▪ Some of the lean oil may vaporize and go out with Ethane (C2H6) and lighter.
▪ To recover lean oil the overhead is charged (connected) to the bottomn of another absorber column and another heavier lean oil called sponge oil.

Question 2

Refinery Gas Plant

■ Process Description?

Answer 2

■
▪ Compression &
phase separation — 
– Heavy Gases like Propane Liquefy
– Heavy Gases like Butane Liquefy

▪ Absorption

3. Debutanizing
4. Depropanizing
5. Deisobutanizing
6. Sponge Absorption

Question 3

■ Feedstock (sources), output & disposition?

Answer 3

■ Feedstock (Sats Gases from distilling column)
▪ Methane (CH4), Ethane (C2H6), Propane (C3H8), Butane (C4H10)
│
■ Output:
▪ Isobutane — Alkylation
▪ Normal Butane — Motor Gasoline Blending
▪ Propane — Liquefied petroleum Gas (LPG)
▪ Ethane — Ethylene or refinery fuel
▪ Methane — Furnance processes, steam boilers
▪ Hydrogen — Hydrocracking, hydrotreating

■ Feedstock (Cracked Gases from Cat Cracker):
▪ Olefins (Ethylene (CH2), Propylene (C3H6), Butylene (C4H8)
│
■ Output:
▪ Ethylene (CH2) — Refinery Fuel System
▪ Propylene (C3H6) — Alkylation
▪ Butylene or Butene (C4H8) — Alkylation