Mass Integration, Equilibrium - Process Design Practice - Lecture Slides, Slides of Process Engineering

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Mass Integration

What is a Mass Exchanger?

Mass Exchanger

OutletComposition: y

outi Lean Stream (MSA)Flowrate:L

j Inlet Composition: x

in j

OutletComposition: x

outj Rich (Waste) StreamFlowrate:G

i Inlet Composition: y

ini

Mass Exchanger–^ A mass exchanger is any direct-contact mass-transferunit which employs a

Mass Separating Agent

(or a

lean phase) to selectively remove certain components(e.g.

pollutants)

from

a^

rich

phase

(e.g.

a^

waste

stream).

-^

Absorption, Adsorption, Extraction, Ion Exchange, ….

Special Cases–^ Raoult’s law for absorption–^ Henry’s law for stripping

Equilibrium 2:

0

(^ ) solute i^

j

p^ T Total y^

x P ^

i^

j^ j

y^

H^

x

^

-^ Mole fraction of solute in gas•^ Vapor pressure of solute at T•^ Mole fraction of solute in liquid•^ Total pressure of gas solubility 0

(^ )

Total(^ ) j^

i P solute H^

y^

T

p^

T

^

-^ Mole fraction of solute in gas•^ Mole fraction of solute in liquid•^ Henry’s coefficient -^ Liquid-phase solubilityof the pollutant attemperature T

-^

Special Cases–^ Distribution function used in solvent extraction

-^

Interphase Mass Transfer–^ For linear equilibrium the pollutant composition in thelean phase in equilibrium with y

can be calculated as:i

Equilibrium 3:4 *

i^

j^ j

y^

K^

x

^

-^ Solute composition in liquid•^ Solute composition in solvent•^ Distribution coefficient

*^

i^

j j

j y^

b x^

 m 

Multistage Contactors–^ Multistage countercurrent tray column

Mass Exchangers – I

Light Phase Out

Heavy Phase In Light Phase In

Heavy Phase Out

ShellPerforatedPlate (Tray)

WeirDowncomer

Multistage Contactors (Continued)–^ Multistage Mixer-Settler System

Mass Exchangers – I

MSAoutWastein^

MSAin Wasteout

Stagewise Columns (Continued)–^ Operating line (material balance)–^ The McCabe-Thiele diagram

Modeling – I

out y

inx in^ y

L outx^ G

^

^

^

in^

out^

out^

in

i^ i

i^

j^ j^

j

G^

y^

y^

L^

x^

x

^

^

in y i o u ty i

in^ x j

o u tx j x^ j

y^ i

O p e ra tin g

L in e E q u ilib riu mL in e

L^ /G^ j^ i

Stagewise Columns (Continued)–^ The Kremser equation•^

Isothermal• Dilute• Linear equilibrium

Modeling – I

ln^

in^ ln

in

j^ i^

i^

j^ j^

j^

j^ i

out^

in

j^

i^

j^ j^

j^

j

j j i

m G

y^

m x

b^

m G

L^

y^

m x

b^

L

NTP

L m G

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

Stagewise Columns (Continued)–^ Number of actual plates–^ Stage efficiency can be based on either the rich or thelean phase. If based on the rich phase, the Kremserequation can be rewritten as:

Modeling – I

NTP^ o NAP

^ ^ ln^1

ln 1

in^

in

j^ i^

i^

j^ j^

j^

j^ i

out^

in

j^

i^

j^ j^

j^

j

j^ i y

j

m G

y^

m x

b^

m G

L^

y^

m x

b^

L

NTP

m GL

^

^

 ^

^

^

^

^

 ^

^

 ^

^

^

^

 ^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

Differential (Continuous) Contactors–^ Countercurrent packed column

Mass Exchangers – II

LightPhase in

HeavyPhase In

Packing Restrainer

RandomPacking

Heavy-PhaseRe-Distributor HeavyPhase Out

Shell PackingSupport

LightPhase Out

RandomPacking

Differential (Continuous) Contactors (Continued)–^ Mechanically agitated mass exchanger

Mass Exchangers – II

Light PhaseOut

HeavyPhase In LightPhase In

Heavy PhaseOut

Shell

Mixer

Continuous Mass Exchangers–^ Height of a differential contactor

Modeling – II

y^

y

H^

HTU NTU

x^

x

H^

HTU NTU

• log (^

in^

out i^

i

y

i^

i^

mean y^

y

NTU

y^

 y ^

^

^

^

^ 

• log

ln in^

out^

out^

in

i^

j^ j^

j^

i^

j^ j^

j

i^

i^

in^

out

mean

i^

j^ j^

j

out^

in i^

j^ j^

j

y^

m x

b^

y^

m x

b

y^

y^

y^

m x

b

y^

m x

b

^

^

^

^

^

^

^

^

^

^

^

^

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Which Car is Cheaper? (Continued)–^ Annual Operating Cost (AOC):

How much to run

Crash Course in Economics 2:5 and maintain the car. $4,000/year

$700/year

$^ vs.

$/year ??? We need to

annualize the fixed cost of the car

Which Car is Cheaper? (Continued)–^ Annualized Fixed Cost (

AFC

)

-^

Total Annualized Cost (

TAC

)

Crash Course in Economics 3:

Initial Fixed Cost

Salvage or Resale Value

AFC

Useful Life Period

TAC

Annualized Fixed Cost

Annual Operating Cost

^