This document summarizes the control design of an industrial grade steady state distillation column and associated production equipment at Vasudha Pharma Chem Limited in Visakhapatnam. It discusses the different types of industrial grade distillation equipment, design and analysis factors to consider, classifications of distillation processes as batch or continuous, components of a distillation column including the rectifying and stripping sections, and general design considerations for the column. The document provides a detailed study of an industrial distillation column used to separate a methanol-water mixture.

1. 1
A REPORT
ON
Control design of industrial grade steady
state distillation column and associated
production equipment
BY
KAUSTUBH TRIPATHI 2014A1PS538P
AT
VASUDHA PHARMA CHEM LIMITED
VISAKHAPATNAM
A PRACTISE SCHOOL I STATION OF

2. 2
A REPORT
ON
Control design of industrial grade steady
state distillation column and associated
production equipment
BY
KAUSTUBH TRIPATHI 2014A1PS538P
PREPARED IN PARTIAL FULFILMENT OF THE COURSE
PRACTISE SCHOOL I
BITS F221
A PRACTISE SCHOOL I STATION OF

3. 3
ACKNOWLEDGEMENTS
The efforts employed for completion of this project would not have been successful
without the kind support and help of many individuals of Vasudha Pharm Chem Ltd. I
would like to extend my hearty thanks to all of them.
I am highly indebted to Mr. Vamsi and Mr. Harsha, whose contribution as coordinators
of the PS Program at the organization was noteworthy in stimulating support which
helped me to complete my project.
I would like to express my deepest gratitude to my mentor and supervisor Mr. K.
Srinivasa Raju sir, Mr. P. Jagadeesh for useful comments, remarks and engagement
through the learning process of this project.
Also, I would like to thank Mr. Rajeev Taliyan, the PS-1 faculty for his smooth and
efficient liaising with the organization and my college which made this opportunity useful
and resourceful for me.
I would also like to thank the PS division authorities in BITS-Pilani for providing me with
this wonderful opportunity. A final gratitude to my parents with whose constant
motivation and trust, this project was initiated and completed to the end.

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BIRLA INSTITUE OF TECHNOLOGY AND SCIENCE
PILANI (Rajasthan)
Practice School Division
Station : Vasudha Pharm Chem Ltd. Centre: Visakhapatnam
Duration: From: 23 May 2016 To: 16 July 2016
Date of Submission: 16 July 2016
Title of the project: CONTROL DESIGN OF INDUSTRIAL GRADE STEADY STATE
DISTILLATION COLUMN AND ASSOCIATED PRODUCTION EQUIPMENT
ID No Name of Student Discipline
2014A1PS538P KAUSTUBH TRIPATHI CHEMICAL ENGINEERING
Name of expert: Mr. P. Jagadeesh Designation: Senior Official, TSD Dept.
Name of PS Faculty: Dr. Rajeev Taliyan
Key Words: Distillation column; Production equipment.
Project Areas: Chemical Engineering
Abstract: The main aim of any industrial unit is to produce products which are chemically stable,
commercially usable and economically viable. To attain this end result, every industry divides its
operation into various departments and to run those departments, it employs concerned skilled
individuals. Production department is the most important department of an industry and is concerned
with largest proportion of industrial activities. Function of a Chemical Engineer is to find out a process
which yields the desired material with minimum cost and in minimum time.
The given project employs use of Distillation Column to yield the desired products. Given project is a
detailed study of control design of industrial grade steady state distillation column. It deals with study
of various components and accessories of a distillation column, reactions employed and efficiency of
each process.
Signature of the Student Signature of the PS faculty
Date: Date:

5. 5
CERTIFICATE
This is to certify that KAUSTUBH TRIPATHI, S/O DR. R.K. TRIPATHI, a student
of B.E. (Hons.) Chemical Engineering, BITS Pilani – Pilani Campus has
successfully completed 52 days (From 23rd May, 2016 to 12th July, 2016) short
internship program at M/s VASUDHA PHARMA CHEM LTD. During the period
of his internship program with us he was found punctual, hardworking and
inquisitive.
---------------------------------- --------------------------------- -------------------------------------
MENTOR KAUSTUBH TRIPATHI DR. RAJEEV TALIYAN
TSD Student PS-1 Instructor
Vasudha Pharma BITS- Pilani Faculty at BITS-Pilani

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CONTENTS
1. INTRODUCTION
2. INDUSTRIAL GRADE DISTISTILLATION EQUIPMENT
2.1. FIXED BOILER
2.2. DYNAMIC DISTILLATION UNIT
2.3. DI-STATIC DISTILLATION UNIT
2.4. DISTILLATION COLUMN
3. DESIGN AND ANALYSIS FACTORS
4. CLASSIFICATION OF DISTILLATION PROCESSES
4.1. BATCH DISTILLATION PROCESS
4.2. CONTINUOUS DISTILLATION PROCESS
5. SCHEMATIC DIAGRAM OF DISTILLATION COLUMN
5.1. RECTIFYING SECTION
5.2. FEED STREAM
5.2.1. SUB-COOLED LIQUID
5.2.2. BUBBLE-POINT LIQUID
5.2.3. PARTIALLY VAPORIZED
5.2.4. DEW-POINT VAPOR
5.2.5. SUPERHEATED VAPOR
5.3. STRIPPING SECTION
5.4. CONDENSER/REBOILER
6. THEORETICAL ANALYSIS OF DISTILLATION COLUMN
7. TYPES OF DISTILLATION COLUMN
7.1. TRAY COLUMNS
7.2. PACKED COLUMNS
8. GENERAL DESIGN CONSIDERATIONS
9. CONCLUSION
10. REFERENCES

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INTRODUCTION
Distillation is one of the most widely used liquid-liquid or vapor-liquid separation
processes. The entire process requires a second phase to be formed so that both liquid
and vapor are present and can make contact while flowing counter currently to each
other in a tray or packed column.
Distillation works according to the principle of removal of heat to exploit differences in
relative volatility of the components to be separated. The component with lower boiling
point and higher volatility gets vaporized and hence leaving behind less volatile
component as bottom product. This method is usually used to separate mixtures with
considerable difference between the boiling points of the constituents. Hence separations
of close-boiling and azeotrope feeds using this method is difficult.
This report deals with study of distillation column, its design and analysis factors, its
working principles along with study of various components associated with the column.
Towards the end, it contains suggestive steps to design an industrial grade distillation
column and the factors to be considered during its operation.

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INDUSTRIAL GRADE DISTILLATION EQUIPMENTS
Industrial grade distillation equipment have 4 basic design concepts:
1. Fixed boiler:
Fixed boiler design of distillation column does not have any rotating part intended for
cleaning the column. These type of columns usually have man-holes or hand-holes
attached to a lift mechanism.
2. Dynamic Distillation Unit:
This type of unit uses an optional scraper. This can either be a fixed boiler or an
externally mounted mobile boiler tank. Scraper blade is usually used in the distillation
columns which treat the encrusting materials. Development of crust on the walls of the
equipment can result in huge inefficiency caused due to improper heat transfer.
3. Di-static Distillation Unit:
This type of column does not utilize any scraper blade. Di-static units can either be fixed
or externally mounted which can be rolled over for cleaning purposes.
4. Distillation Column:
This is usually a tall tower erected using cemented structures. Such units are usually
used for separation of very specific chemicals. They yield an end product with very high
purity.
This report deals with study of distillation columns, about 16-18 m high and used for
separation of methanol-water mixture.

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DESIGN AND ANALYSIS FACTORS
While designing any industrial equipment, it is very important to analyze its operational
factors and utility. Design factors are mainly governed by the type of components, type
of processes, flow profile of the components, efficiency factors, spatial factors and final
products. While designing a distillation column, following factors are always considered:
 FEED FLOW RATE.
 FEED COMPOSITION.
 FEED TEMPERATURE, PRESSURE AND PHASE.
 DESIRED DEGREE OF SEPARATION.
 PRESSURE DROP IF IT IS A VACUUM OPERATION.
 MINIMUM AND ACTUAL REFLUX RATIO.
 MINIMUM NUMBER OF EQUILIBRIUM STAGES AND ACTUAL NUMBER OF
EQUILIBRIUM STAGES.
 TYPE OF CONDENSER: TOTAL, PARTIAL OR MIXED.
 DEGREE OF LIQUID REFLUX SUB-COOLING.
 TYPE OF REBOILER: PARTIAL OR TOTAL.
 TYPE OF TRAYS OR PACKING.
 COLUMN HEIGHT.
 COLUMN DIAMETER.
 COLUMN INTERNALS AND MATERIAL OF CONSTRUCTION.
 HEAT AVAILABILITY AND CHEMICAL REACTIVITY OF FEED COMPONENTS.

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CLASSIFICATION OF DISTILLATION PROCESSES
Distillation columns are of two types based on mode of operation, namely, batch
distillation and continuous distillation.
BATCH DISTILLATION PROCESS
In batch distillation, the feed to the column is introduced batch-wise. The column is first
charged with a ‘batch’ and then the distillation process is carried out. When the desired
task has been accomplished, next batch of feed is fed into the reactor. Vasudha Pharma
Chem Limited uses Batch Distillation Process to produce its final products. Although the
columns are capable of being operated under both batch and continuous conditions, but
the organization uses all its columns in a batch mode.
CONTINUOUS DISTILLATION PROCESS
In continuous distillation columns, continuous feed stream is employed to input the
products. No volunteered interruption are made during the operation of a continuous
distillation column. Continuous columns are capable of handling high throughputs. Apart
from this, parallel variations can come handy in a continuous distillation column, such as
multiple feed points and multiple output points. Continuous distillation columns are used
in most of petroleum and chemical industries.
SCHEMATIC DIAGRAM OF DISTILLATION COLUMN

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According to the diagram, a distillation column has following major components to be
studied about-
1. R Section or Rectifying Section.
2. Feed Stream.
3. S Section or Stripping Section.
4. Condenser/Reboiler.
Following section deals with detailed study of the various sections of a distillation
column.
1. Rectifying Section-
Rectification section is the part of column which lies above feed point. The process
taking place in Rectifying Section is called rectification. During this process, vapor phase
is continuously enriched in the lighter component which makes the final product. A
condenser is used at the top of rectifying section to condense these vapors to liquid. To
achieve further purification, this liquid is sent again into the rectifying column in the
form of reflux.

12. 12
2. Feed Stream-
There are various ways in which feed stream can be given to a distillation column. Feed
stream considerations are important in determining the operating lines for rectifying and
stripping sections. Knowledge of operating lines is important because it provides us with
information regarding theoretical number of stages.
Feed streams are broadly of 5 types-
A. Sub-Cooled Liquid.
Sub-Cooled feed contains completely liquid feed
cooled to a very less temperature, but more than its
freezing point. Thus as soon as feed is given into the
column, the vapors going up from stripping section
get cooled and converted into liquid.
B. Bubble-Point Liquid.
Bubble point liquid contains feed which is heated up to its
bubble point. There are no traces of vapor in the feed and
the rising vapors inside the column also remain unaltered
in the composition.

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C. Partially Vaporized.
Partially vaporized feed contains both liquid and vapors
given as input to the distillation column. Liquid feed
settles to bottom in the stripping section, while vapor
feed goes to the top in the rectifying section.
D. Dew-Point Vapor.
Dew point vapor contains purely vaporized feed.
Entire feed goes into the rectifying section along with
vapors already inside the column.
E. Superheated Vapor.
Superheated Vapor feed contains vapor heated to a very
high temperature. Due to this some of the liquid
descending from the rectifying section gets vaporized
and combines with the rising vapors.

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3. Stripping Section
Stripping section is the part of column which lies below feed point. The process taking
place in Stripping Section is called stripping. During this process, heavier component is
stripped off and concentrated liquid phase forms the bottom product. A reboiler is used
at the bottom of stripping section to vaporize the liquid. At each separation stage (each
tray or a theoretical stage in the packing), the vapor enters from the stage below at a
higher temperature while the liquid stream enters from the stage above at a lower
temperature. Heat and mass transfer occur such that the exiting streams (bubble point
liquid and dew point vapor at the same temperature and pressure) are in equilibrium
with each other.
4. Condenser
Condenser is an equipment which is used at the top of the distillation column to
condense the vapor and separate the components at the top into distillate and reflux.
There are two types of condensers which are used with a distillation column: total
condenser and partial condenser. In a total condenser, all vapors leaving the top of the
column is condensed to liquid so that the reflux stream and overhead product have the
same composition. In a partial condenser, only a portion of the vapor entering the

15. 15
condenser is condensed to liquid. In most cases, the condensed liquid is refluxed into
the column and the overhead product drawn is in the vapor form. On the other hand,
there are some cases where only part of the condensed liquid is refluxed. In these
cases, there will be two overhead products, one a liquid with the same composition as
the reflux stream while the other is a vapor product that is in equilibrium with the liquid
reflux.
Total Condenser Partial Condenser

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THEORETICAL ANALYSIS OF DISTILLATION COLUMN
Now, we shall study the theoretical equations governing the distillation column. Let us
define the variables.
F: Total feed rate.
ZF = Mole fraction of component in feed.
XD = Mole fraction of component in distillate.
XB = Mole fraction of component in the bottom product
D = Distillate flow rate.
B = Bottom flow rate.
VB = Boil-up Ratio.
Writing the theoretical equations for rectifying section:
Mass Balance:
F = D +B
Material Balance:
ZFF =XDD + XBB

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TYPES OF DISTILLATION COLUMN
There are various types of distillation columns each varying with respect to efficiency
and utility. Following are the most widely used types of distillation columns-
TRAY COLUMNS take the
advantage of difference in
pressure and temperature to
separate the components. In a
tray column, the weir maintains
and holds a level of liquid. Entry
of the liquid is from the down-
comer of the plate which is right
above it. The vapor comes from
bottom with sufficient pressure
that it overcomes the pressure
exerted due to height of the liquid
in the tray. Thus in this way mass
and energy transfer takes place
between the two components.
In PACKED COLUMNS, solid
packing is used to facilitate
contact in between the two
phases. Packed columns are the
most efficient distillation columns
because they are able to perform
well at low pressure and also at
low liquid and vapor packing. At
high flow rates, their efficiency
are heavily compromised due to
heavy fouling and corrosive
conditions. Packed Columns are
capable of providing a contact
area of more than double that of
tray columns.

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GENERAL DESIGN CONSIDERATIONS
While designing an industrial grade distillation column there are two factors which are
looked upon very closely, a process design and a mechanical design. With the help of
process design factors, we calculate the number of theoretical stages, diameter of the
column and height of the tower. Mechanical design focuses on internal structure of the
tower and arrangement of heat exchanging equipment. Apart from these two, there are
several other factors which are to be considered. A few of them are safety and
environmental requirements, column performance, economics of the design and other
parameters, which may constrain the work.
Separation sequences are set of tasks which have to be chronologically followed to
design any separation equipment. These separation sequences depend on the relative
volatility and concentration of each component in the feed. Few of the design rules that
are followed are:
Once the separation sequence is accepted, calculations are done to determine the critical
parameters. In general, the steps included in distillation calculations are summarized as
following:
1. Material balance for the column
2. Determination of tower operating pressure and/or temperature.

19. 19
3. Calculation of the minimum number of theoretical stages.
4. Calculation of minimum reflux rate.
5. Determination of the operating reflux rate.
6. Determination of number of theoretical stages.
7. Selection of internal organization of the column. (Tray or packings)
8. Calculation of tower diameter and height.
Most of the industries use Packed Distillation Columns. Hence, this report analyzes the
design considerations of Packed Columns. The design concepts of packed columns are
given below:
1. Most of the packed towers have a lower pressure drop as compared to tray towers.
2. Packing in packed columns is often retrofitted into tray towers to increase capacity
and extent of separation.
3. For gas flow rate of 500 ft3/minute (14.2 m3/minute), 1 inch (2.5 centimeter)
packing is used and for gas flow rate of 2000 ft3/minute (56.6 m3/minute) or
more, 2 inch (5 cm) packing is used.
4. Ratio of diameter of tower to diameter of packing should at least be 15.
5. Since there is a possibility of plastic being deformed, plastic packing should be
limited to an unsupported depth of 10-15 feet (3-4 meter) while metal packing can
withstand 20-25 feet (6-7.6 meter).
6. Liquid distributors should be placed every 20 feet along the height.
7. For redistribution, there should be 8-12 streams per sq. ft. of tower area if tower
has a diameter more than 3 feet.
8. Packed columns should operate at a conditions of nearly 70% flooding.

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CONCLUSIONS
This project was concentrated along the lines of study and designing a steady state
distillation column. We have studied, estimated and successfully applied an effective and
efficient control design procedure for distillation columns using steady state operating
models. The steps of the design procedure are:
1. Develop design basis.
2. Select control factors.
3. Select operating factors.
4. Test run the modal.
5. After successful test run, manufacturing can be started.

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REFERENCES
1. Tolliver T. L. and McCune L. C., "Distillation Column Control Design Based On
Steady State Simulation", ISA Transactions, Vol. 17, No. 3, 1978, Pages 3-10.
2. Seader, J.D., Henley, E.J., “Separation Process Principles,” 2nd Edition, Wiley India
Pvt. Ltd., New Delhi, 2006.
3. http://kolmetz.com/pdf/EDG/ENGINEERING%20DESIGN%20GUIDELINES%20-
%20distillation%20column%20-%20Rev%2004%20web.pdf