Chemical Engineering June 2019 - 55

resulting value proposition) of the model is not lost on
the end owner, and the model itself is well-designed
and fit for purpose (that is, Figure 1C is a preferable
operating model over Figure 1B).
Echoing a recent call for improving communications
throughout the chemical engineering community, this
article draws attention to the crucial role communication
has on model development and its many uses [1].
Conceptualization
Assuming the underlying chemical engineering problem
or challenge has been carefully defined by its owner,
a first step in the development cycle is to identify the
key phenomena that will lead to using the appropriate
equations to describe the process. In the case of a
model that relates to evaporative drying, for example,
the main chemical engineering phenomena considered
would be heat and mass transfer (Figure 2).
The conceptualization step, and the next (model
building), will ensure that a sharable support (document)
for knowledge retention is created by the very
process of model development.
Model building
Following conceptualization, the identified key phenomena
can be translated in different mathematical
ways. For instance, the transport of water out of solid
materials during drying can be described using either
diffusion or capillary movement (or both) [Equations (1)
and (2)].
Drying and diffusion theory:
(FROM BLEED PUMP)
NEUTRALIZ
1200 GAL
(1)
Drying time using the capillary theory:
IMMERSION HEATER
METERING PUMP (OPERATING)
ACID STORAGE TANK
CHEMCIAL ADDITION PUMP (OPERATING)
AI
105A
AI
104B
ORP
500 GAL. CAPACITY
H2SO5
105B
AI
ORP
TO CAUSTIC FILL
(PI2)
8
Where:
w = Total moisture, kg
t = Time, s
DL = Diffusion coefficient (liquid phase), m2/s
l = Thickness, m
w0 = Initial moisture, kg
weq = Equilibrium moisture, kg
tf,cap = Drying time based on the capillary theory, s
Qs = Density of the dry solid, kg/m3
hfg = Latent heat of vaporization, J/kg
h = Heat transfer coefficient, W/m2K
Tabs = Absolute air temperature, K
T'S = Evaporative surface temperature, K
PI
8
WASH WATER
(FROM BLEED PUMP)
3 "
3/4 "
FAL
1
104A
AI
DPI
1
DPT
1
PACKING
50 GAL. CAPACITY
1st JET
IMMERSION HEATER
36 " GAS INLET
(EMERGENCY)
12 " GAS INLET
ACID STORAGE TANK
(NORMAL)
AI
104B
ORP
H2SO5
METERING PUMP (STAND-BY)
4 " SPARE
PT
8
The most appropriate description will depend largely
on the nature of the material and the amount of water
to be removed. The decision will be supported and
validated by either purposefully designed experiments
or historical data.
WASH WATER
MANWAY
3 "
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
DPI
1
DPT
1
PT
2
MIST ELIM.
PI
2
75,000 GAL MAX. CAPACITY
Call us: (973) 947-8787
Email us: info@crcleanair.com
Address: Six Campus Drive
Parsippany, NJ 07054
AI
PT
1
PI
1
TE
4
TE
2
3/4 "
IMMERSION HEATER
LIQUID SEPARATOR TANK
96 " Ø x 10' TALL
1st JET
AI
2
1
6 "
T I
4
T I
2
pH
pH
pH
AI
1
12 " GAS INLET
FAL
1
FT
1
11
2 "
FE
1
For details visit adlinks.chemengonline.com/73855-11
36 " GAS INLET
Visit us at: www.CRCleanAir.com
1st JET
6 "
RECYCLE
PUMP A
TIC
2
CAUSTIC FILL
(FROM CHEM. STORAGE TANK)
MAG
TE
TE
TIT
TIT
4 "
4 "
4 "
3 3
1 1
PT
7
PI
7
4 "
AI
AI
4
3
PT
4
OR
OR
3/4 "
4 "
4 "
2 "
METERING PUMP (OPERATING)
ORP
1st JET H2SO4
FT
1
FE
1
NEUTRALIZATOIN TANK
1200 GAL. CAPACITY
MAG
IMMERSION HEA
TE
TE
3
1
TIT
3
TIT
1
PT
8
PT
2
MIST ELIM.
LIQUID EFFLUENT
PI
2
PT
1
NAOH
CHERMICAL ADDITION PUMP (STAND-BY)
METERING PUMP (STAND-BY)
IMMERSION HEATER
ORP
NAOH STORAGE
TANK FARM
50 GAL. CAPACITY
ORP
104A
AI
IM
H2SO4
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LIQUID EFFLUENT
TO CAUSTIC FILL
NAOH
TANK FARM
POLLUTANTS
HCL / CL2
HF / HBr
SO2
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105B
AI
ORP
CHERMICAL ADDITION PUMP (STAND-BY)
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CHEMCIAL ADDITION PUMP (OPERATING)
AI
105A
ORP
NAOH STORAGE
500 GAL. CAPACITY
IMMERSION HEATER
PI
1
TIC
1
PT
5
BY-PASS
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Chemical Engineering June 2019

Table of Contents for the Digital Edition of Chemical Engineering June 2019
