PROCESS OPERABILITY

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CHEMICAL ENGINEERING 4N04
PROCESS OPERABILITY Ensuring that the plant has
the capacity and flexibility to achieve a range
of operating conditions safely, reliably,
profitably and with good dynamic performance.
We already know engineering principles - now,
lets apply them and learn more about practice!
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CHEMICAL ENGINEERING 4N04
PROCESS OPERABILITY Ensuring that the plant has
the capacity and flexibility to achieve a range
of operating conditions safely, reliably,
profitably and with good dynamic performance.
Some engineers prefer the term Robust Design.
The two terms have the same general meaning.
3
PROCESS OPERABILITY Ensuring that the plant has
the capacity and flexibility to achieve a range
of operating conditions safely, reliably,
profitably and with good dynamic performance.

• Topic includes nine lessons and one workshop,
  each in a separate PowerPoint file
• What will we learn in this lesson?
• - What is operability?
• - Why operability is essential?
• - How is operability integrated into design
  procedure?
• - What are eight key operability issues?
• Learning goals and skill outcomes
• Subsequent lessons cover each issue in some detail

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What is Operability?
From the simplest to most complex process, we
must think about operability!
I need to regulate the flow, but how complex
should the equipment be? Does the need for
operability affect this decision?
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What is Operability?
CLASS WORKSHOP
What do the following words have in common?
Music
Love
Operability
Happiness
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What is Operability?
CLASS WORKSHOP
Difficult to define exactly, but we know when we
have achieved or fallen short!!
Music
Love
Operability
Happiness
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What is Operability?
CLASS WORKSHOP
Difficult to define exactly, but we know when we
have achieved or fallen short!!
PROCESS OPERABILITY Ensuring that the plant has
the capacity and flexibility to achieve a range
of operating conditions safely, reliably,
profitably and with good dynamic performance.
Still vague, so we will define a eight categories
and see many examples for each.
Operability
8
Operability essential?
A PROCESS DESIGN PROCEDURE

• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment
• Construct and start up

Operability prevents this inconsistency!
Operate the plant over a range of conditions,
including many operating points and transitions
between them
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Operability essential?
PROCESS DESIGN WITH OPERABILITY
The design procedure should ensure that the plant
is operable, that it functions well. This
requires a specification that addresses a range
of conditions.

• 1. Changes to desired operations,e.g., feed,
  production rate and product quality
• - We need to match production rate to sales
• We often produce multiple products and some
  products are made at different qualities (grades)
• We often process various feed materials

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Operability essential?
PROCESS DESIGN WITH OPERABILITY
The design procedure should ensure that the plant
is operable, that it functions well. This
requires a specification that addresses a range
of conditions.
2. Disturbances - Many external variables
change from their assumed base case values. We
refer to these as disturbances - really normal
variation in the plant. Example are feed
composition, ambient temperature, cooling water
temperature, catalyst deactivation, heat
exchanger fouling, etc.
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Operability essential?
PROCESS DESIGN WITH OPERABILITY
The design procedure should ensure that the plant
is operable, that it functions well. This
requires a specification that addresses a range
of conditions.
3. Changes to production schedule The market
demands and transportation systems change
frequently, and the process operation must
respond quickly. Changes can be rapid and require
major modifications to plant operation.
12
Operability essential?
PROCESS DESIGN WITH OPERABILITY
The design procedure should ensure that the plant
is operable, that it functions well. This
requires a specification that addresses a range
of conditions.
4. Uncertainty in design models Our
predictions are uncertain - not useless, just
contain some errors. Examples include
equilibrium, rate processes, and efficiencies. We
compensate for these errors through
flexibility. If we rely on perfect models, the
plant will not likely operate as expected.
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Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IN THE DESIGN
PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
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Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

We must define the range of operations and goals
to achieve before we begin the design! Design
limited to the base case is not likely to be
satisfactory.
The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
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Operability in Design?
Operability Class Workshop Identify key aspects
of a design specifications that could change and
whose ranges must be defined in a Design Basis
Memorandum.
reactors
compression
refrigeration
separation
products
feeds
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Operability in Design?
Operability Class Workshop Identify key aspects
of a design specifications that could change and
whose ranges must be defined.
Some examples are given below (the lists are not
comprehensive)

• Feeds
• compositions
• rates
• prices
• contracts (must use?)
• impurities
• crude oil - salt
• fuels - sulfur
• polymer - acetylenes

Products composition specifications rates prices,
f(x, flow)? contracts (must satisfy?)
Effluents rates allowed compositions
allowed limits penalties
Energy utilities fuels steam electricity hydrog
en oxygen

• Environment
• ambient temperature
• cooling water
• air compressor
• steam tracing
• disturbances
• rain storms

Integrated Units supply of material supply of
energy destination for material destination for
energy
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Operability in Design?
We have to known where we are going before we can
design!

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

The design must define the range of operations to
be achieved. We can accept less than full
production rate or top efficiency for extreme
situations. We must document specifications and
range or operations and review with all
stakeholders!
The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
18
Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

This might influence the range of operations! For
example, a fluidized bed reactor could have a
smaller range of flow than a packed bed.
The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
19
Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

This might influence the range of operations! For
example, the addition of a recycle stream might
allow a wider range.
The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
20
Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

Some of the flowsheet variables, such a
distillation feed location and reactor volume,
influence the achievable range of operations.
The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
21
Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• Design Procedure
• Set goals and design specifications
• Select process technology
• Define process structure (sequence)
• Simulate the flowsheet
• Design equipment

The flowsheet typically involves basic ME
balances, equilibrium and rate processes. It
does not consider practical issues for achieving
the operation.
Equipment design has a very strong influence on
the range of plant operation. Again, satisfying
the base case is not sufficient.
Equipment design achieves the base case flowsheet
(plus other concerns). This sets the capacity
of the plant.
22
Operability in Design?
OPERABILITY WHEN DO WE INTRODUCE IT IN THE
DESIGN PROCEDURE?

• The principle sins associated with flowsheets
  used for economic evaluation are sins of
  omission. . Other frequently omitted items
  include
• Storage tanks
• Surge tanks
• Duplicated equipment (for reliability)
• Start-up equipment
• Emergency safety equipment
• .

Valle-Riestra, J.F.(Dow Chemical Co.), Project
Evaluation in the Process Industries,
McGraw-Hill, New York, 1983 (pg 169)
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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Operability eight topics?
OPERABILITY INVOLVES MANY ISSUES What Will We Do
In The Course?
The design procedure involves balancing many
objectives, including the eight operability
issues. Sometimes, we call this multi-objective
design or multi-disciplinary design. One way to
combine disparate objectives is through
economics, but objectives like safety and product
delivery and quality must be satisfied,
regardless of cost. (If they cannot in a
profitable manner, we do not proceed with the
project.)
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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Operability eight topics?
OPERABILITY INVOLVES MANY ISSUES What Will We Do
In The Course?

• We will
• Learn eight of the most common operability issues
  
• Understand typical designs
• through many class
• workshops
• Apply our learning to a major course project
  performed in teams
• Build for the future 4W04 and engineering
  practice

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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Operability eight topics?
OPERABILITY INVOLVES MANY ISSUES Why is
Operability in a required course?

• We will learn how to learn about a process.
  This is a general skill that
• Requires all prior knowledge (courses)
• - Great opportunity to reinforce learning and
• apply to a process that interests you
• Motivates learning new aspects of equipment
• Can be applied to essentially any process

Plant operations
Plant design
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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Operability eight topics?
OPERABILITY INVOLVES MANY ISSUES Can be applied
to essentially any process?
Sample of some projects completed by recent 4N04
Groups

• Milk power plant
• Ammonia plant
• Boiler water treating
• Refrigeration system with cooling tower
• Pump selection
• Haemodialysis
• Penicillin plant

• Waste water treating
• Liquid-liquid separation
• Petroleum distillation
• Desalinization by reverse osmosis
• Wine making (industrial)
• Water treating

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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Learning goals and outcomes?
OPERABILITY INVOLVES MANY ISSUES What are the
Topic Learning Goals?
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Key Operability issues 1. Operating window 2.
Flexibility/ controllability 3.
Reliability 4. Safety equipment protection 5.
Efficiency profitability 6. Operation during
transitions 7. Dynamic Performance 8.
Monitoring diagnosis
Operability eight topics?
OPERABILITY INVOLVES MANY ISSUES What will you
be able to do?
Identify the key operability issues in a process
and design the process flowsheet and equipment to
achieve good process operability. You will not be
limited to approaches discussed in the class
examples. You will be able integrate this
analysis with engineering economics when
selecting the best designs.