GAS ABSORPTION

Question 1

A separation process where a component in a gas mixture
is separated by contact with a liquid solvent or solution

Answer 1

GAS ABSORPTION

Question 2

Types of Absorbers

Answer 2

➤ Packed column
➤ Plate column

Question 3

Provides continuous contact between vapors
and liquid phases while the plate column brings the two phases into
contact on stage wise basis.

Answer 3

Packed column

Question 4

Should be high in order to increase rate of
absorption and decrease amount of solvent needed.

Answer 4

Gas solubility

Question 5

Solvent should have low vapor pressure to
reduce loss of solvent in the gas leaving the absorption
column

Answer 5

Volatility

Question 6

Should be non-toxic, non-flammable and
chemically stable

Answer 6

Solvent

Question 7

There are two types of gas absorption:

Answer 7

chemical and
physical absorption.

Question 8

Reaction between the absorbent
and solute. Examples include using NaOH as an absorbent to dissolve acid gas, dissolving CO2 and H2S in aqueous
solution of MEA.

Answer 8

Chemical gas absorption

Question 9

No significant chemical reactions between the absorbent and solute. Examples include almost all gas absorptions that use water or hydrocarbon oils as absorbent.

Answer 9

Physical absorption

Question 10

Achieves the necessary intimate contact between vapor and liquid phases for effective mass transfer by having the liquid flow down the column over some sort of distributive solid particle countercurrent to the rising vapors. When vapors and liquid are fused counter currently.

Answer 10

Packed column

Question 11

Packed Column: Classification

Answer 11

➤ Random Packing
➤ Stacked Packing

Question 12

For the tower to operate the actual mass velocity of the gas (Gg or Gy) must be lower than the flooding mass velocity of Gg < Gf

Answer 12

Flooding Mass Velocity (Gas)

Question 13

COMPARISON BETWEEN PACKED AND PLATE COLUMN

Answer 13

SCALE: For column diameter of less than approximately 8 ft, it is more usual to employ packed towers because of high fabrication cost of small trays. But if the column is very large then the liquid distribution is problem and large volume of packing and its weight is problem.
* PRESSURE DROP: Pressure drop in packed column is less than the plate column. In plate column there is additional friction generated as the vapor passes through the liquid on each tray. If there are large number of Plates in the tower, this pressure drop may be quite high and the use of packed column could effect considerable saving.
* LIQUID HOLD UP: Because of the liquid on each plate there may be a Urge quantity of the liquid in plate column, whereas in a packed tower the liquid flows as a thin film over the packing.
* SIZE AND COST: For diameters of less than 3 ft. packed tower require lower fabrication and
material costs than plate tower with regard to height, a packed column is usually shorter than the equivalent plate column