PROCESS CONTROL

IN CHEMICAL
ENGINEERING
Agung Nugroho
Universitas Pertamina
Content
1. Introduction to Process Control
2. Mathematical modeling
3. Laplace Transformation and Transfer Function
4. Dynamic Behavior of 1st and 2nd order system
5. Dynamic behavior of higher order systems
6. Development of Empirical models from process data
7. Feedback Controllers
8. Stability of closed-loop control systems
9. Controller design: Tunning PID Controller, FF, ratio, cascade
controller

2
Text Book
Utama:
■ Thomas E. Marlin, Process Control: Designing
Processes and Control Systems for Dynamic
Performance, McGraw-Hill, 1995
■ D. E Seborg, T. F. Edgar, D. A. Mellichamp, Process
Dynamics and Control, 4th ed. John Wiley & Sons,
2011.
■ Stephanopoulos, George, Chemical Process
Control: An Introduction to Theory and Practice,
Prentice-Hall International, 1984
Pendukung:
■ Luyben, William L., Process Modeling, Simulation
and Control for Chemical Engineers, Second
Edition, McGraw-Hill International Edition, 1990
■ Carlos A. Smith, Armando B. Corripio, Principles
and Practice of Automatic Process Control, John
Wiley & Sons, 1985, ISBN 0-471-88346-8
■ Kuo, Benjamin C., Automatic Control Systems, Sixth
Edition, Prentice-Hall International Editions, 1991
Grading:
1. Tugas (15%)
2. Kuis (10%)
3. UTS (25%)
4. UAS (25%)
5. Tugas komputasi (25%)

Time Schedule
■ CE 6 Selasa 07.00 – 08.40
■ CE 6 Rabu 15.00 – 15.50
■ Absensi dari SIUP, jangan sampai terlambat.

4
WHY HAVE A PROCESS CONTROL COURSE?

• When I run a kinetics experiment, how do I

maintain the temperature and level at desired
values?

• How do I manufacture products with consistently

high quality when raw material properties
change?

• How much time do I have to respond to a

dangerous situation?

Every engineer needs basic knowledge about control.

Many exciting career opportunities exist for a
technical specialist.

5
 WHY NOW FOR THE CONTROL COURSE?

• We started with steady-state analysis because it is

easier and important.

• We are building expertise in fundamentals (fluids,

heat transfer, thermo, etc.) and process units
(distillation, CSTR, etc.). Now we have examples
that need control!

• We need to master control before integrating our

knowledge in process design?

It’s a perfect time to learn how to “drive” the chemical

process. With this insight, we will be able to design plants
that can be controlled safely and produce high quality products.

6
 Introduction to
Process Control
■ Process → The conversion of feed materials to products using chemical
and physical operations.

Input output
Process

■ Goal of plant operation:

– Safety
– Production schedule
– Product quality
– Maximum profit
7
Classification of processes:

■ Based on time:
– Steady-state (no variations with time)
– unsteady-state (variations with time).
■ Based on flowing streams:
– Continuous processes,
– Non-Continuous processes : batch, semi-batch.

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■ Examples:
Continuous processes

Non-Continuous processes

9
Definition of
Process Control
■ What is process control?
– Monitor the process status
– To drive the process to desired condition
– By manipulating adjustable handles
■ How to monitor process status?
– Measure important process variables by sensors
– Estimate the important variables through indirect
measurements
■ What are adjustable handles?
– Process variables manipulated by actuators
– Ex: flow rate by control valve, motor speed by inverter, etc

10
Seven (7) Control Objectives of
Process Control
1. Safety
2. Environmental protection
3. Equipment protection
4. Smooth operation
5. Product quality
6. Profit
7. Monitoring and diagnosis

12
 EXAMPLE PROCESS: FLASH SEPARATION

Let’s discuss
this process
T6 P1
Vapor
product

Feed T1 T2
T5 P  1000 kPa
Methane T  298 K
Ethane (LK)
Propane F1 T4 T3 L1
Butane
Pentane

F2 F3

A1
Liquid
Process Steam product
fluid Product composition
13
 SEVEN CONTROL OBJECTIVES

Give example
1. Safety

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3

6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

14
 SEVEN CONTROL OBJECTIVES

High pressure
1. Safety in drum is
dangerous Vapor
2. Environmental T6 PC
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

15
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

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 SEVEN CONTROL OBJECTIVES
To flare
1. Safety Never release
hydrocarbons
Vapor
2. Environmental to atmosphere T6 P1
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

17
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

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 SEVEN CONTROL OBJECTIVES

1. Safety No flow could

damage the
2. Environmental
Vapor
pump T6 P1
product
Protection

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 LC
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

19
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

20
 SEVEN CONTROL OBJECTIVES

Always keep
1. Safety the production
rate smooth Vapor
2. Environmental T6 P1
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation FC T4 T3 L1
production rate

5. Product quality
F2 F3

6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

21
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

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 SEVEN CONTROL OBJECTIVES
Achieve
product
1. Safety
composition
2. Environmental by adjusting T6 P1
Vapor
Protection the heating product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3

6. High profit AC
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

23
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

24
 SEVEN CONTROL OBJECTIVES

Use the least

1. Safety
costly heating
2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit AC
Liquid
Process Steam product
Product composition
fluid
7. Monitoring &
diagnosis

25
 SEVEN CONTROL OBJECTIVES

1. Safety Give example

2. Environmental T6 P1
Vapor
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
L. Key
fluid
7. Monitoring &
diagnosis

26
 SEVEN CONTROL OBJECTIVES

1. Safety Calculate & plot

key parameters,
Vapor
2. Environmental e.g., UA. T6 P1
Protection product

3. Equipment T5
T1 T2
protection
Feed
4. Smooth operation F1 T4 T3 L1
production rate

5. Product quality
F2 F3
6. High profit A1
Liquid
Process Steam product
L. Key
fluid
7. Monitoring &
diagnosis
Heat transfer coef.
(UA)
time
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 SEVEN CONTROL OBJECTIVES

1. Safety
All seven must be achieved. Failure to do so
will lead to operation that is
2. Environmental unprofitable or worse, unsafe.
Protection

3. Equipment T6 P1
Vapor
protection product

4. Smooth operation T5
T1 T2
production rate
Feed
5. Product quality F1 T4 T3 L1

6. High profit

7. Monitoring & F2 F3
diagnosis A1
Liquid
Process Steam product
L. Key
fluid

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Through control,
we can achieve:
■ Safe operation
■ Satisfying environmental constraints
■ Economic benefit
■ Increased production level
■ Reduced raw material cost
■ Enhanced product quality
■ Extended equipment life
■ Potential benefits of improved process control

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 WHERE IS CONTROL DONE?

Sensors, local
indicators, and
valves in the process

Displays of variables,
calculations, and commands
to valves are in the
centralized control center.
Shows an older-style
control panel
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 WHERE IS CONTROL DONE?

Creative Commons License, see http://en.wikipedia.org/wiki/File:Nuclear_Ship_Savannah_-_Reactor_Control_Room_-

_Center_and_Left_Panels.jpg

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 WHERE IS CONTROL DONE?

Sensors, local
Central control room indicators, and
valves in the process

Displays of variables,
calculations, and commands
to valves are in the
centralized control center.
Shows a modern, computer-
based control panel
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WHERE IS CONTROL DONE?

Photo courtesy of Worsley Alumina and Honeywell 33

HOW IS CONTROL DESIGN DOCUMENTED?

• Piping and instrumentation (P&I) drawings provide

documentation.
• We must use standard symbols.

FC

F = flow

TC LC L = level
A P = pressure
T = temperature
…..
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Identification letters in instrumentation and process
control:
Identification letters in instrumentation and
process control:

Practical
Instrumentation for Automation and Process Control
for Engineers and Technicians 36
Example

37
Instrumentation Symbol

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Signal symbol
■ Sinyal elektrik (electric) atau
elektronik, normalnya antara 4 dan
20 mA. Jarang menggunakan 10 –
50 mA atau 1 – 5 V atau 0 – 10 V.

■ Sinyal pneumatic atau tekanan

udara, normalnya 3 – 15 psig.
Jarang menggunakan 6 – 30 psig
atau 3.0 – 27 psig.

■ Sinyal digital atau diskret (nol dan

satu).

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42
Types of Process Variable
■ Manipulated variables (MV) → The process variables that can
be adjusted in order to keep the CV at or near their set points.
Input
■ Disturbance Variables (DV) → Process variables that affect
the controlled variables but cannot be manipulated.
■ Controlled variables (CV) → The process variables that are
controlled. Output
– Set point → the desired value of controlled variable
■ Uncontrolled variable → Process variable that cannot be
controlled.

Remarks:
■ All important CV must be identified and measurable
■ MV must have significant impacts on CV (MV usually affect
the CV’s)
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Example of Process Variable in
Heat Exchanger
Hot water Oil

Oil water

Manipulated
variables Flow rate Hot water

Temperature of Hot oil Controlled

variables
Temperature of Hot
Disturbances water
Number of Tube
Flow rate of oil enter HE
HE
Number of passes Uncontrolled
Heat loss variables

Temperature of oil
enter HE
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 Example of Process Variable in
Distillation Column
Feed flow rate F Distillate composition xD
Disturbances
Feed composition z Bottom composition xB
Controlled
Level reflux drum MR variables
Reflux flow rate R Level base MB

Reboiler heat QR Pressure P

Manipulated Distillate flow rate D

variables Tray 15 temperature
Bottom flow rate B
Tray 5 temperature Uncontrolled
Cooling water flow rate Fw variables

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 Example: Stirred tank heater

DV
CV

MV 46
How to control a process?

■ Control objective:
– Maintain controlled variable (CV) at its set point,
despite disturbances.

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SEE YOU ON NEXT
LECTURE