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FLUID-SOLID
SEPARATION
PROCESSES
(ADSORPTION PROCESSES)
ENGR. DR. MOHD IRFAN HATIM MOHAMED DZAHIR
What is adsorption?
Adsorption is a process in which one or more
components of a gas or liquid stream are adsorbed on the
surface on the solid adsorbent and a separation is
accomplished.
Operation of adsorption process:-The adsorbent is usually in the form of small particles in a
fixed bed.
-The fluid is passed through the bed and the solid particles
adsorb components from the fluid.
-When the bed is almost saturated, the flow through the
bed is stopped and the bed regenerated thermally or by
other method that can promotes desorption.
-The adsorbed component (adsorbate) is thereby
recovered and the solid adsorbent is ready for another
cycle of adsorption.
Liquid-phase adsorption
Removal of organic compound from:1) water or organic solution,
2) colored impurities from organics,
3) and various fermentation products from fermentor
effluents
Example of separation:-Paraffin from aromatics
-fructose from glucose using zeolite adsorbent.
Gas-phase adsorption
1) Removal of water from hydrocarbon gases
2) Sulphur compounds from natural gas
3) Solvent from air and other gases
4) Odor from air
Physical properties of adsorbent
-In the form of small pellets, beads, or granules
ranging 0.1 mm to 12 mm in size.
-Adsorbent particle has a very porous structure,
with many fine pores and pore volumes up to 50%
of total particle volume.
-Adsorption occurs as a monolayer although several
layers sometimes occur.
-Physical adsorption (van der Waals) is the type of
force presence between the adsorbed molecules
and the solid internal pore surface and readily
reversible.
Commercial adsorbent,
1.Activated carbon (SA of 300 – 1200 m2/g)
2.Silica gel (SA of 600 to 800 m2/g)
3.Activated alumina (SA of 200 – 500 m2/g)
4.Molecular sieve zeolites
5.Synthetic polymer or resins
BATCH ADSORPTION
Commonly used to adsorb solute from liquid solution when
the quantities treated are small in amount.
Material balance on the adsorbate is,
qFM + cFS = qM + cS
qF = Initial concentration of solute adsorbed
q = final concentration of solute adsorbed
cF = Initial feed concentration
c = final equilibrium concentration
DESIGN OF FIXED-BED ADSORPTION COLUMNS
Cb – break-point
concentration
Cb/Co of 0.01 to 0.05
Time equivalent to total or stoichiometric capacity of packed-bed tower tt
(represented by total shaded area)
Tu time equivalent to the usable capacity or the time at which the effluent
concentration reaches its maximum permissible level, tu is very close to tb
Numerical integration of
both equations can be
solved using a
spreadsheet!
HB is the length of bed used up to the break point,
tu/tt is a fraction of total bed capacity
The length of unused bed HUNB,
Total bed length,
Adsorption
Problems
Assignment (To be submitted before 12 noon, 19 March 2012)