Download - IPC Lecture 1
CHE334 Instrumentation and
Process Control (IPC)
By Dr. Maria Mustafa
Department of Chemical Engineering
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Week 1Chapter 1 Introduction to Inst and PC
Main Topics
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Chapter 1 An introduction to Instrumentation and
Process Control
Unit Online
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Unit description:
Describe principles and concepts related to process
control & instrumentation.
Applications
Definitions
Identifications
Learning resources/
Textbooks: Lecture Notes
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Recommended Textbooks
George Stephanopoulos, Chemical
Process Control : An introduction
to Theory and Practice , Economy
Edition
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Recommended Textbooks:
Dale E. Seborg, Duncan A.
Mellichamp Thomas F. Edgar,
Francis J. Doyle, Process
Dynamics and Control, John
Wiley,NewYork,2011
Reference Book
Coulson & Richardson’s, Chemical Engineering, Vol 3, Third
Edition, 2006
W.L. Luyben, “Process modeling, Simulation and Control
for Chemical Engineers”, 2nd Edition, McGraw Hill, New
York, 1990.
D. Coughanowr, S. E. LeBlanc, “Process Systems Analysis
and Control”, McGraw-Hill Third Edition, Boston, 2009.
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Unit Outline
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Assessment Information
First Sessional Test10%
Second Sessional Test 15%
Quizzes/Assignments 25%
Terminal Examination 50%
The minimum pass marks for each course shall be 50%. Students obtaining less than 50% marks in any course shall be deemed to have failed in that course.
Any Questions?
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Chapter 1 Introduction
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Learning Outcomes:
Describe principles and concepts related to process control &
instrumentation.
Definitions
Design Control Problems statements
Incentives/ Applications
Identifications
Process Control
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Control in process industries refers to the regulation
of all aspects of the process involved. in chemical
industry.
Control Problem Design
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In chemical engineering we have different chemical units
For example: Reactor, Distillation Column, Pumps
To constitute chemical plant, we have to assemble these
units
Objectives of chemical Plant
Input to chemical plant is raw material using different available
source of energy produce product in most economical way.
Requirements Of Chemical Plant
Safety
Production specification
Environmental Regulations
Operational Constraints
Economics
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Control Problem Design
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To meet these objectives, we need to satisfy requirement
Safety Rector which is designed to operate at 100 bar pressure, to maintain
this limit we need external intervention so that reactor operate below this limit
Production Specification
Quantity and Quality
Environmental Requirements /Regulations
There are number of federal laws which enforce to maintain environment. It is enforce to maintain the conc. of chemical in the effluent stream SO2 existed to the environment
Waste water returned to the environment
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Operational Constraints
Plant have certain Constraints inherent to operation
Distillation Column should not be flooded
Tanks should not overflow or go dry
Temperature of catalytic reactor should not exceed upper limit.
Economics
To control operating conditions to such a optimium level so
that we have minimum operating maximium profit etc
Incentives or Applications of Process
Control
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To meet all these requirement, an external intervention is required means we need to devise a control system
Three important issues which can be handled by control system
I. Influence of external disturbances
II. The Stability of chemical process
III. Performance of chemical Plant
Basic Aim of control system
I. To suppress Influence of external disturbances
II. To ensure the Stability of chemical process
III. To optimize the performance of chemical Plant
Identification
Process, Problem, Process Variables
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Process
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Process as used in the terms process control and
process industry, refers to the methods of changing or
refining raw materials to create end products.
Process Control
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Process control refers to the methods that are used to
control process variables when manufacturing a product.
Goal of Process Control
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Process engineers are often responsible for the safe and
satisfactory operation of chemical processes. As these
processes become larger scale and/or more complex,
the role of process automation becomes more and
more important.
Goal :
To learn how to develop, design and
tune controllers for the automated
operation of chemical processes.
Process Control
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Human Aided Control vs Automated Control
Incentives of Chemical Process Control
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Suppressing the influence of external disturbances
Ensuring of safety of Chemical Process
Optimizing the performance of a chemical process
Reduce Variability
Suppressing the influence of
External Disturbances
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Identify the variables
Develop Control Mechanism
Controlling the operation of Stirred Tank Heater
Example
Control Objectives 1. To keep temperature
at desired value.2. To keep volume or
level of the liquid in the tank at desired value
Suppressing the influence of External
Disturbances
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Expected Disturbance Input Variables ( Temperature, Flow rate)
Practical case input variable may change
So to maintain the temperature we have to design Control system
Stirred Tank Heater
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Fi, Ti
h
F, T
T
Q
Control Mechanism
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Fst
Fi, Ti
h
F, T
T
Q
Thermocouples
Controller
SetPoint
T-+ e
e> 0 , more steam is
required
e< 0 , less steam is
required
Ensure Stability of a Chemical
Process
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“X” returns automatically to
steady state / desired state
Response of Unstable process
Required external Intervention
to Time
X
to Time
X
AB
c
• “X” returns automatically to
steady state / desired state
• Response of stable process; Self-
regulating
• No external intervention required
External
Disturbanc
e
X = T , CA
X is disturbed at t = to
External
Disturbanc
e
Case Study
Controlling the Operation of Unstable
Reactor
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CSTR with Cooling Jacket
cA, Ti, Fi
Tci, Fc
Tco, Fc
cA T, F
A B ( exothermic reaction)
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Optimize the Performance of a Chemical
Process
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After achieving main objective
Safety
Production Specifications
Optimize the Performance of a Chemical Process
Case Study II
Optimizing the performance of Batch
Reactor
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cA, Ti, FiStream
Controller
Condenser
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A B C (endothermic reaction)Reaction1 2
Desired undesired
Optimizing the performance of Batch
Reactor
Q
Qmin
Qmax
tr Time
Steam flow rate
0
Minimium utilization
Maximum utilization
Classification of Variables
Variables that are extensively used in the Process Control
Varibles
Input
Disturbance/Load VARIALE
Manu plated or adjustable /control
variable
Output
Measured Variable/controlled
Vriable
Unmeasured d Variables
Common Terminologies
Process Variables: Conditions of process fluid that can
change manufacturing process in someway.
Input variable which denotes the effect of the
surroundings on the chemical Process.
Output Variable which denote the effect of the
chemical process on the surroundings.
Input Variables
Manipulated Variables
Disturbances
Output Variables
Measured Output
Unmeasured Output
Next Task
We will take different examples or case studies
We will select / indentify the variables
Example of Liquid Tank
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Fi
h
F
Controlled Varible : h
Input Variable
• Fi
Output Variables
• F (if not manipulated)
• V or h
Objective is to maintain the level of liquid in
tank “h”
Paring the CV and manuplated variable, which variable can be adjustable
CV MV
h Fi , F
Example of Stirred Tank Heater
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Fst
Fi, Ti
h
F, T
T
Q
Input Variable : Fi, Ti, Fst
Output Variables:
• F ( if not manipulated)
• V or h
• T
Objective is to maintain the level and
Temperature of liquid in tank i.e. “h” & “T”
CV MV
h Fi , F
T Fst
F
Z
mB
mD
VB
DxD
BxB
R xD
Reboiler
Condenser
Reflux Drum
(Stephanopoulos, 1984)
Example of Distillation
CV MV loo
p
xD R 1
xB VB 2
mD D 3
mB B 4
Terminologies Control Configuration
A control configuration is the information structure that is used to connect the available measurements to the valuable manipulated variables.
Two types of CC SIS0 = single input –single output configuration ,
example controlling the level of the liquid in the tank
MIMO= multiple input – multiple out configuration = Example controlling the level and temperature of the liquid in the tank by changing output flow rate and steam flowrate.
TerminologiesGeneral Type of Control Configuration
FeedBack Control Configuration Use the direct measurements of the controlled variable to adjust the manipulated variables. The control action is taken after the disturbances effect the controlled output variables.
Control Configuration
Feedforward Control Configuration Use the direct measurements of the disturbances to adjust the manipulated variables: Objective is to keep output variable at desired value. It anticipates the control action to be taken.
Control Configuration
Inferential Control Configuration: Uses secondary measurements ( because the controlled variables can not be measured ) to adjust the manipulated. The control objective is to keep the un measured controlled variable at desired levels.