PowerPoint Sunusu

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Mass Transfer Zone and Breakthrough
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FEED Solute(adsorbable) Solvent (
FEED
EFFLUENT
Adsorber packed bed section
YO
XO
YO mass solute/mass solvent XO mass
solute/mass adsorbent
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Constant pattern behavior, X vs t waves
X
t2
t6
t5
t3
t4
t1
Y
Yo
X-t Concentration waves
Favorable isotherm
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Proportionate behavior
Unfavorable Isotherm
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XO
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Breakthrough curve concentration(dimensionless)
of solute in column effluent
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Length of Unused Bed (LUB) Concept
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Stoichiometric front
Velocity of stoichiometric front velocity of
the mass transfer front
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At any time t, the length of the equilibrium
section will be Zs V t At time ts , the
stoichiometric front reaches the end of column,
thus   Z V ts  By definition, at breakthrough
time tB   Zs V tB  Therefore LUB Z Zs V
(ts tB)
LUB Z (ts tB)/tS (1)
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A solute balance over unit cross sectional area
of large scale bed gives   Gs (Yo Ya) t Zs
?b ( Xe Xo ) (2) Where Gs mass flux
of solvent, mass/(area)(time) Yo concentration
of solute in feed, mass solute/ mass solvent Ya
concentration of solute in fluid in equilibrium
with Xo Xo residual solute concentration on
adsorbent after regeneration, mass solute/mass
adsorbent Xe concentration of solute on
adsorbent in equilibrium with solute
concentration in feed( Yo), mass solute/mass
adsorbent  From which Zs can be calculated. Then
Z ZSLUB (3)
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A still simpler design equation for calculating
amount of adsorbent required for fixed-bed
adsorption

• Gs (Yo Ya) t (Z ?b Xe ) f
• Per unit cross sectional area
• Amount of solute in cycle time t equilibrium
  capacity of the bed X fractional saturation of
  the bed working capacity
• f fractional saturation of the bed accounts for
• Presence of mass-tranfesfer zone at the end of
  bed at brakthrough
• Incomplete regeneration
• Aging of adsorbent
• Temperature rise due to heat of adsorption
• Other capacity reducing factors

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Process cycles Temperature Swing Adsorption
(TSA)
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Process cyclesPressure Swing Adsorption(PSA)
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Process cycles Inert Purge Cycle
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Process cycles Displacement-Purge Cycle
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Fluidized-Bed Adsorption System
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Simulated Moving Bed Adsorption
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Typical Properties of Activated Carbon Adsorbents
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Typical Properties of Adsorbent-Grade Silica Gel
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Typical Properties of Adsorbent-Grade Activated
Alumina