Page 27 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

P1: LDK Revised Pages
Encyclopedia of Physical Science and Technology EN001H-01 May 7, 2001 16:18

24 Absorption (Chemical Engineering)

L Liquid flow rate, lb/h (kg/h) x fm Film factor, given by Eq. (8b)
L Liquid flow rate, lb mole/h (kmol/s) y Mole fraction solute (in bulk-gas phase,
(Fig. 12 and Eq. 33 only) unless otherwise subscripted)
l Liquid component flow rate, lb mole/h y Mole solute in gas per mole of rich gas
(kmol/s) entering the absorber
L M Molar liquid-phase mass velocity, y A Mole fraction solute A (in bulk-gas phase,
2
2
lb mol/(h ft ) [kmol/(s m )] unless otherwise subscripted)
L Molar solute-free solvent mass velocity, y ∗ Mole fraction solute in bulk-gas in
M
2
2
lb mol/(h ft ) [kmol/(s m )] equilibrium with solute concentration in
m Slope of equilibrium curve = dy /dx, bulk-liquid
∗
dimensionless y ∗ Mole fraction solute in bulk-gas in
A
N Number of stages in a stagewise contactor equilibrium with solute concentration in
N Mass transfer rate across interface, lb bulk-liquid
mole/h (kmol/s) (Fig. 12 and Eq. (32) only) y BM Logarithmic-mean inert-gas concentration
Molar flow rate of solute A per unit between bulk-gas and interface, defined by
N A
2
interfacial area, lb mol/(h ft ) Eq. (6a)
2
[kmol/(s m )] y ∗ Logarithmic-mean inert-gas concentration
BM
N B , N C ,... As N A , but with respect to solute B, C, ... between bulk-gas and value in equilibrium
Number of gas-phase mass-transfer units, with bulk-liquid
N G
dimensionless y fm Film factor, given by Eq. (8b)
Number of liquid-phase mass-transfer y ∗ Film factor, given by Eq. (8d)
N L
fm
units, dimensionless δ Film thickness, ft (m)
N OG Number of overall gas-phase mass-transfer µ Liquid viscosity, cP [kg/(s m)]
3
3
units, dimensionless ρ Density, lb/ft (kg/m )
P Pressure, atm (kPa) σ Surface tension, dyn/cm (N/m)
o
p Solute partial pressure in bulk gas, φ Ratio k L /k , reaction enhancement factor,
L
atm (kPa) dimensionless
o
Q Heat removal rate, Btu/h (kJ/s) φ ∞ Ratio k L /k when H a =∞, dimensionless
L
r A Volumetric reaction rate of component A, ψ Ratio of water to liquid density,
3
3
lb mol/(h ft ) [kmol/(s m )] dimensionless
Volumetric reaction rate of component B,
r B
3
3
lb mol/(h ft ) [kmol/(s m )] Subscripts
T Temperature, F( C) 0 Liquid inlet to stage contactor
◦
◦
t Parameter defined by Eq. (8d), indicating 1 Column bottom (differential contactor)
degree of counter-diffusion 1 Stage 1 (Top stage in a stagewise
Vapor velocity, based on tray area less the
U nf contactor)
area at the bottom of the downcomer, at the 2 Column top (differential contactor)
flood point, ft/s (m/s) 2 Stage 2 (Stagewise contactor)
Superficial vapor velocity, ft/s
U s A Component A
V Gas flow rate, lb mole/h (kmol/s) ave Average for the column
v Gas component flow rate, lb mole/h B Component B
(kmol/s) C Component C
x Mole fraction solute (in bulk-liquid phase G Gas phase
unless otherwise subscripted) i Interface
x Mole solute in liquid per mole of j Component j
solute-free solvent entering absorber L Liquid phase
x A Mole fraction solute A (in bulk-liquid N Stage N (bottom stage in a stagewise
phase, unless otherwise subscripted) contactor)
x ∗ Mole fraction solute in bulk-liquid
A n Stage n
inequilibrium with solute concentration in
bulk-gas Superscripts
x BM Logarithmic-mean inert-solvent I At the interface
concentration between bulk liquid and L Liquid
interface, given by Eq. (6b) v Vapor (or gas)