Summary Week 2
I. Multicomponent : Vapor-Liquid Equilibrium
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Vapor-Liquid Equilibrium Data à Txy
Diagrams (cont'd)
-
Bubble Point Calculations (assuming Raoult's Law)
find Tbp such that f(Tbp)=0
-
Dew Point Calculations (assuming Raoult's Law)
find Tdp such that g(Tdp)=0
II. Multicomponent : Solid-Liquid Equilibrium
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Data: Solubility data at different temperatures.
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Usually given in mass fraction, e.g.
solubility of AgNO3 in H2Oat 20oC = 222
g AgNO3/100 g H2O.
-
See Figure 6.5-1, page 266.
III. Multicomponent : Vapor-Solid Equilibrium
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Adsorption : molecules in the vapor phase attaches to the surface
of the solid adsorbent.
-
Data:
Adsorption isotherms data
-
usually plots X*A as function of pA
where X*A is the mass ratio of adsorbate
A to adsorbent, say activated carbon,
and pA is the partial pressure
of adsorbate A in vapor phase.
-
Langmuir Isotherms - a model used to estimate X*A
.
where a and KL are parameters which are functions
of temperature.
IV. Multicomponent : Liquid-Liquid Equilibrium
Situation: There are two liquid phases, a raffinate
phase and an extract phase, in which a third component called the
solute is distributed within each phase.
Cases:
a) Raffinate and Extract phases are completely immiscible.
Data: distribution coefficent = ratio of
mass fraction in one phase to the other phase.
For example, for solute Acetone, the distribution coefficient in
Chloroform/Water system is given as
b) Raffinate and Extract phases are partially miscible
Data: ternary diagram (see e.g. Figure 6.6.-1
on page 274 for Acetone-MIBK-Water system)
The diagrams usually contain TIE lines which determine the corresponding
pair
of equilibrium compositions in the raffinate-rich phase and extract-rich
phase.
V. Mixing Line Principle
When mixing two streams, one flowing at a rate of G mols/h
with composition vi (for each component i) and another
stream flowing at a rate of H mols/h with composition wi,
The resulting mixture will flow at a rate M=G+H mols/h
with composition zi, in which zi will
lie in a line segment connecting vi and wi.
This page is maintained by Tomas B. Co ( tbco@mtu.edu
). Last revised 3/18/2000.
Tomas B. Co
Associate Professor
Department of Chemical Engineering
Michigan Technological University
1400 Townsend Avenue
Houghton, MI 49931-1295
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