Absorption & indusrial absorber,Gas Absorption,Equipments,Absorption in chemical Reaction,Absorption in Packed Tower,Absorption for counter current,Choice of Solvent,Continuous Contact Equipment,Height Equivalent to Theoretical Plate,HETP
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Absorption & indusrial absorber
1.
2. It is a mass transfer operation in which one or
more gas solutes is removed by dissolution in a
liquid.
The inert gas in the gas mixture is called “carrier
gas”.
In the absorption process of ammonia from air-
ammonia mixture by water, air is carrier gas,
ammonia is „solute” and water is absorbent.
3. An intimate contact between solute gas and
absorbent liquid is achieved in a suitable
absorption equipment, namely, tray tower,
packed column, spray tower, venture scrubber,
etc.
Desorption or stripping operation is the reverse
of absorption. Absorption operation is of two
types; physical and chemical.
𝑆𝑆𝑆𝑆𝑆𝑆 +𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 = 𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆
+
𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆.
4. Absorption and stripping (as well as
distillation) operations are usually carried out
in vertical, cylindrical columns or towers in
which devices such as plates or packing
elements are placed.
The gas and liquid normally flow
countercurrently, and the devices provide the
contacting interfacial surface through which
mass transfer takes place (cocurrent flow is also
possible from economic standpoint).
5. Operations in which one or more components of a
gas phase are absorbed into a liquid phase are
common throughout the chemical process industries
and frequently serve to achieve desired reactions
among components in the two phases (Lee & Tsui,
1999).
Such operations are often called reactive absorption
because of the combination of reaction and
absorptive mass transport.
As an example, in the absorption of carbon dioxide
by caustic soda, the carbon dioxide reacts directly
with the caustic soda.
6. An advantage of absorption plus reaction is the
increase in the mass-transfer coefficient.
This may be due to a greater effective
interfacial area.
The process hydrodynamics can also be
directly involved via correlations for the hold-
up, pressure drop, and mass transfer
coefficients, etc.
ADVANTAGE :
7.
8. Generally , the gas which to be absorbed in the
liquid which is sparged to the bottom of the
column with the help of carrier gas.
The carrier gas which has insoluble in the liquid
solvent.
The liquid solvent is entered at the top side
countercurrently.
At the some height,the packing material is set
for mass transfer operation where absorption
occurs.
9. The packing either be Regular or Random
based on industrial requirement.
Abbility of absorption mainly depends on
choice of solvent however it will be good
prefered for gases or not.
12. The basic expressions for material balances and
their graphical interpretations will be
presented for countercurrent flow (a similar
method may be used for cocurrent flow).
The gas stream at any point in the tower
consists of G total moles/hr, made up of
diffusing solute A of mole fraction yA, partial
pressure pA, or mole ratio YA, and non-
diffusing, essentially insoluble gas GS
moles/hr. The relationships among these are:
13. Similarly the liquid stream consists of L total
moles/hr, containing xA mole fraction soluble
gas, or mole ratio XA, and essentially non-
volatile solvent LS moles/hr. The relationships
among them are:
Thus the material balance (for y and x subscript
A is omitted):
which is rearranged for the gas phase mole
fraction of y as:
14. It is easy to prove that the second parts of the
last two equations are equal, by writing a
material balance on the whole equipment
which can be rearranged as follows:
15. The liquid and gas compositions in a packed
tower changes continuously throughout the
height.
The composition of solute from entry to exit of
the packed tower is represented by operating
line and every point indicates some location in
the packed tower.
On the other hand, in tray tower, few points
(number of trays) in the operating line
represents the conditions in the trays.
16. Height Equivalent to Theoretical Plate::::::
For a specified separation job, in packed tower,
the height of packing is to be determined and
in tray tower, numbers of ideal trays are
determined.
The ratio between packing height to number of
trays required for the same separation is called
height equivalent to theoretical plate (HETP)
17.
18. • Relatively low pressure drop
• Capable of achieving relatively high mass-
transfer coefficient and high mass transfer rate
• Increasing the height and/or type of packing or
try numbers capable of improving mass
transfer without purchasing a new piece of
equipment
• Relatively low capital cost
• Relatively small space requirements
19. • Fiberglass-reinforced plastic construction
permits operation in highly corrosive
atmospheres.
• Ability to collect particles as well as gases
• Collected substances may be recovered by
distillation
20. • Possibility of creating water (or liquid) disposal
problem (remark: IPPC)
• Product collected wet
• Particulates deposition possibly causing
plugging of the bed or the plates
• Fibreglass-reinforced plastic is sensitive to
temperature
• Relatively high maintenance cost
• Must be protected from freezing (if operated in
outside)