Chemical Engineering May 2017 - 61

 58.85°C  112 kcal/h.m2.°C =
177,960 kcal/h.
Maximum steam consumption in
the coil = 177,960 kcal/h/509.5 kcal/
kg = 350 kg/h.
Maximum load of steam to each
layer of coil = 350/2 kg/h = 175 kg/h.
Having selected two layers of
coils, let us now come to the selection
of the number of coil passes in
each layer. If one pass arrangement
in each coil layer was used, then the
maximum velocity of steam in 25
mm coil works out to 46 m/s, which
is rather high. Therefore we should
have two layers of coils, each having
two passes (as in Figure 4, bottom).
Concluding remarks
This article emphasizes the need for
heating or cooling in storage tanks.
For certain highly viscous liquids,
temperatures inside some tanks
sometimes need to be maintained
at elevated levels for ease of pumping,
while in some cases, lower temperatures
are required to avoid polymerization,
exothermic reactions or
product degradations.
The various options available for
heating or cooling have been described.
The factors to be considered
while selecting the right option
are also described. The various design
parameters to be considered
during design are explained. A sample
calculation is also illustrated. The
finer aspects of coil design and engineering
are also presented.
Note: The content of the article is
based on the authors' personal views
and their own published research. n
Edited by Gerald Ondrey
References
1. Schroyer, J. A., Understand the Basics of Steam Injection
Heating, Chem. Eng. Prog., May, 1997, pp. 52-55.
2. Dream R. F., Heat Transfer in Agitated Jacketed Vessels,
Chem. Eng., January, 1999, pp. 95-96.
3. Catani S. J., Control System Cuts Tanks Heating and
Cooling Costs, Chem. Eng., August 24, 1981, pp. 129.
4. Kumana J. D. and others, Predict Storage Tank Heat
Transfer Precisely, Chem. Eng. March 22, 1982, pp.
127-132.
5. http://www.spiraxsarco.com.
6. Cowan C. T., Choosing Materials of Construction for
Plate Heat Exchangers - Part II, Chem. Eng., July 7,
1975, pp. 102-104.
7. Green, D. W., Perry, R. H., " Perry's Chemical Engineer's
Handbook, " 7th Edition, Chapter 11, Page 21,
McGraw-Hill, New York, 2004.
Authors
Apurba Lal Das is a senior principal
engineer at Air Liquide Global E&C
Solutions India Pvt. Ltd. (A24/10,
Mohan Cooperative Industrial Estate,
Mathura Road, New Delhi
110044, India, Phone:
+91-1142595365,
Email: apurbalal.das@
airliquide.com). He joined Air Liquide
in September 2007, and has 12
years of experience in process engineering,
with exposure to various technologies, such as
petroleum refineries, petrochemicals, sulfur-recovery gas
cleaning and more. He also has experience in plant operations.
Das earned his B.Tech degree from Haldia Institute of
Technology and M.Tech from I.I.T. Kanpur. He has life membership
to the Indian Institute of Chemical Engineers.
Siddhartha Mukherjee is the director
- Technology at Air Liquide
Global E&C Solutions India Pvt. Ltd.
(same address as above;
Phone:+91-11-42595365, Email:
siddhartha.mukherjee@airliquide.
com). He joined Air Liquide in June
1993, and has 27 years experience
in the design, engineering, precommissioning
and commissioning of
refineries and petrochemicals plants and general process
engineering. Prior to this, Mukherjee worked as an environmental
engineer with Development Consultants Ltd.
(Kolkata), doing various environmental impact assessment
projects involving thermal power plants. he earned his
B.Tech and Ph.D. Ch.E. degrees from I.I.T. Kharagpur. He
has life memberships to the Institute of Engineers and the
Indian Institute of Chemical Engineers. He has a number of
publications in national and international journals. He is
listed in the Marquis Who's Who in Science and Engineering.
He is also an Air Liquide Group International Expert.
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