Diapositiva 1

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Program for North American Mobility in Higher
Education (NAMP) Introducing Process Integration
for Environmental Control in Engineering
Curricula (PIECE)
Module 15 Process Control and Process
Integration Tier 2
Created at Universidad de Guanajuato École
Polytechnique de Montréal
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This module is divided in three essentials
complements, it will demonstrate the
relationship between the use of PI tools in
order to design a process and the control
strategies.
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Structure

• Tier one
• Basic Concepts About Process Control
• Tier Two
• Use of PI tools and especially dynamic simulation
  to address control strategies
• Tier Three
• Analysis of a real process.

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• Index
• Tier one
• Comparison between Steady Sate and Dynamic State.
• Important Definitions about dynamic state.
• Dynamic Models.

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• Index
• Tier two
• Relationship between Process Design and Process
  Control
• Dynamic Effect on recycle Structures.

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Tier 2
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Tier 2
Objective

• Understand the interaction between process
  design and process control.
• Understand the effect of recycle structures on
  dynamic behavior.

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Process Control in a Integrated Perspective
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Any process starts with
Identification and creation of potential
opportunities to satisfy societal needs and to
generate profit.
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Manufacturing process
Natural Resources
Basic Chemical products
Basic Chemical products
Manufacturing process
Industrial Products
Basic Chemicals industrial Products
Manufacturing process
Consumer Products
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The next step is
Process Creation
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Process design starts with the synthesis of a
process to convert raw material into desired
products
Product Streams
Feed Streams
?
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Process Flowsheet
Is a diagrammatic representation of the process
steps using icons to represent process units and
arrows to represent connections among them
Product Streams
Feed Streams
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It is common the presence of recycles (process
integration) because its advantages to recover
energy. However is important to know how they
affect the dynamic properties.
Simulation Steady State
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Simulation
Is a mathematical model of the process that
attempts to predict how the process would behave
if it were constructed or modified
Product
Feed
New Operating Condition
Operating Condition
Steady Sate Simulation the operating conditions
are changed to others ones in order to evaluate
new operating sceneries
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Having the process flowsheet the next step is to
evaluate the process control configuration.

• How to control the process.

• Effect of the recycle in process dynamic

• Effect of the heat integration in process
  dynamic.

Dynamic State Simulation allows to test different
control strategies and to know the influence of
changes in the process design on the dynamic
behavior.
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The role of Control Process in Process Design
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Controllability Analysis

• RGA
• Niderlinski Index
• Condition Number

Resiliency Analysis

• Relative Disturbance Gain
• Disturbance Cost
• Disturbance Condition Number

Previous
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Effect of recycle
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Recycle Structures
These structures are used often in process
plants to return material for reprocessing and to
recover energy from effluent streams trough heat
exchanger.
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Fresh feed is heating using the stream leaving
the reactor
Heat Recycle
This stream goes trough a heat exchanger in order
to recover heat
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Block diagram for this system
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Now using block diagram algebra to determine el
behavior of the integrated system transfer
function is
Characteristic Equation
Poles of overall system are different to the
poles of the individual units. The stability of
this system cannot be guaranteed even if each
individual system is stable.
Block Diagram
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Now defining
Gain
Time Constant
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Time constant and gain have been increased in the
reactor with recycle
Performing a Dynamic Simulation to know the
dynamic behavior
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500
500
100
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Why ?
Increase in T0
Affects Tf
Affects TR
The output is reinforced through the recycle
exchanger
There is a positive feedback
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According the previous slides

• The time constant and the steady state gain of
  the overall system with recycle can be changed
  substantially from their values without recycle.
• Recycle can alter the stability and possibility
  for a periodic behavior of the overall system,
  because it affects the poles of the overall
  system.
• This effect should be considered when the
  process control is developed because the time
  constant is related with the speed of response of
  the process.

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QUIZ
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1.- The effect of a positive feedback is not
desirable because
a) Its actions tends to increase the error from
desired.
b) Its action tends to reduce the error from
desired.
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2.- If time constant increases its value , it
implies
a) A slow systems response when changes on
manipulated variables are made to produce changes
on controllable variable.
b) A faster systems response when changes on
manipulated variables are made to produce changes
on controllable variable.
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Correct Answer
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Correct Answer
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CONGRATULATIONS!
Now you have finished Tier 2