Absorption Flashcards
(13 cards)
What is absorption?
Liquid solvent is used as a separating agent.
“Absorption adds…” ie liquid becomes dirty and gas is cleaned
What is stripping?
Insoluble gas is used as separating agent.
“Stripping subtracts” ie. Liquid is cleaned
What does the rate of mass transfer rely on?
Concentration in gas and liquid
Solubility of components in liquid
Mass transfer coefficients of components in both phases
Available area for mass transfer
Equation relating to pressure and Henry’s constant?
Partial pressure of B = H B * x B
Assumes low concentration of B
Give three examples of gas absorption.
Absorption of CO2 from NG and flue gas.
Removal of H2S and CO2 using MEA
Removal of pentane-butane from refinery gas mixture with heavy oil
Name four assumptions for operating lines in absorption.
- Heat of absorption is negligible.
- Isothermal operation.
- Solvent is nonvolatile.
- Carrier gas is insoluble.
Why are heat of absorption and isothermal operation just assumptions?
If temperature increased, Henry’s law constant would change.
What does nonvolatile solvent assume?
Low temperature
High pressure of gas
What does insoluble carrier gas assume?
L and G flowrates are constant
Assumptions for Kremser equation?
1% Dilute solutions
L/G is constant (constant flow rates)
Isothermal
Isobaric
Negligible heat of absorption
Straight equilibrium line
What is light component?
m»_space; L/G
Equilibrium near bottom
What is key component?
m = L/G
Absorption throughout column
What is heavy component?
m «_space;L/G
Equilibrium near top
