CHE334 Instrumentation and

Process Control (IPC)

By Dr. Maria Mustafa

Department of Chemical Engineering

1

Week 1Chapter 1 Introduction to Inst and PC

Main Topics

2

Chapter 1 An introduction to Instrumentation and

Process Control

Unit Online

3

Unit description:

Describe principles and concepts related to process

control & instrumentation.

Applications

Definitions

Identifications

Learning resources/

Textbooks: Lecture Notes

4

Recommended Textbooks

George Stephanopoulos, Chemical

Process Control : An introduction

to Theory and Practice , Economy

Edition

5

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.

6

Unit Outline

7

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?

8

Chapter 1 Introduction

9

Learning Outcomes:

Describe principles and concepts related to process control &

instrumentation.

Definitions

Design Control Problems statements

Incentives/ Applications

Identifications

Process Control

10

Control in process industries refers to the regulation

of all aspects of the process involved. in chemical

industry.

Control Problem Design

11

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

12

Control Problem Design

13

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

14

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

15

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

16

Process

17

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

18

Process control refers to the methods that are used to

control process variables when manufacturing a product.

Goal of Process Control

19

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

20

Human Aided Control vs Automated Control

Incentives of Chemical Process Control

21

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

22

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

23

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

24Fs

Fi, Ti

h

F, T

T

Q

Control Mechanism

25

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

26

“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

27

CSTR with Cooling Jacket

cA, Ti, Fi

Tci, Fc

Tco, Fc

cA T, F

A B ( exothermic reaction)

28

Optimize the Performance of a Chemical

Process

29

After achieving main objective

Safety

Production Specifications

Optimize the Performance of a Chemical Process

Case Study II

Optimizing the performance of Batch

Reactor

30

cA, Ti, FiStream

Controller

Condenser

30

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

35

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

36

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.