INTEGRITY™
Pinch Technology Software for the Process Engineer
INTEGRATE SIMPLY
…. preliminary design of heat exchanger
networks in new plant
Minimum System Requirements:
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
PC running Windows 95, 98, or NT 4.0 Service
Pack Three or higher.
Use INTEGRITY™ to
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Develop simple integration schemes
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Consider realistic exchanger technology
486 or greater processor.
2MB hard disk space.
Minimum 16MB RAM, 32 MB recommended.
Minimum display requirements: Minimum
screen resolution 800 X 600, recommended
Available via CD-ROM or
the Internet. For Web
delivery, customers must
download a zipped file
and install the application locally
screen resolution is 1024 X 678, minimum color
depth 256 colors.
Don’t Miss Design Opportunities
ESDU has developed software tools that can be used in integrated plant design. They offer
an improvement over traditional tools in that they produce output that is simple to follow
and easily understood. ESDU helps you keep network design ‘in touch’ with reality.
ESDU’s INTEGRITY™ software program provides a simple, rapid, and straightforward route
for the design of heat exchanger networks in new plants. It offers the advantages of
considering a network design that keeps close to plant layout, controlling expensive piping
costs, and designing safer more easily understood plants. This simplicity provides you a
cost-effective means to combat expensive plant design and maintenance issues. With
INTEGRITY™ you can:
# Design networks which keep close to layout -control piping costs, design safer plant
# Eliminate need to model heat exchangers as ‘black boxes’
# Keep network design in touch with reality
# Optimise network design elements during synthesis
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Industry Situation
Process Integration is an important means of improving the energy efficiency of industrial
processes and refers to the systematic approach resulting in efficient process design with
integrated use of energy and water within and between process operations on-site.
ESDU has developed a number of computer programs that can be used in integrated plant
design. INTEGRITY™ allows the user to
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
“By using suitable software, such as ESDU’s
INTEGRITY™, it is possible to quickly establish which
parts of a plant offer the best opportunities for energy
saving. A new structure that allows these savings to
# Determine utility consumptions, utility cost, network area
needs, network capital cost and total annual cost at a
specified minimum temperature approach.
be made can then be established. Detailed design
# Generate the composite curves and HDS diagram.
changes can be identified by trading-off energy saving
# Specify stream velocities and pressure drops rather than
against investment. The result is a detailed design that
assumed heat transfer coefficients to produce estimates of
directly complies with the economic constraints speci-
how the network area is distributed across the various
fied for the project. These trade-off calculations can be
undertaken using standard spreadsheets. Sophisticated
and expensive software is not needed.”
process streams.
# Undertake optimisation (Range Targeting). INTEGRITY™ and
has been set up for easy implementation of the Repetitive
Targeting approach to network design developed by ESDU.
--Graham P olley
Technology Transfer
Process Integration traditionally has been restricted to energy
Management
use minimization of process plant, but extended by ESDU to
include equipment capital cost reduction and options for safer
plant design (by localization of key components to minimize complexity).
Process Integration is based on a systematic and practical understanding of the process
heat and material flows. ESDU aids the practicing engineer in getting up-to-speed and
familiar with these topics.
Product Driver
The aim of effective process integration is the optimum trade-off between energy and
capital cost minimization. Confidence that the best possible design has been achieved
is more easily achieved, today, using ESDU’s process integration tools and guidance.
Understanding heat recovery and water reuse opportunities, and ensuring that process
equipment is correctly located within a plant design are key to realizing savings in
practice. ESDU data helps you unlock the data you need for safe, confident designs.
Product Description
Application of Process Integration offers users the ability to:
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Make better use of capital, energy, and water resources
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Reduce operating costs
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Meet the challenge of sustainability
Process Integration is applicable at all process engineering design stages including:
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On-going improvement of existing sites
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Upgrades and major retrofits
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Conceptual design of new plants
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Development of new technology
INTEGRITY™ INTEGRATE SIMPLY
Network Design Using Traditional Methods:
Plant appears highly energy efficient, but
actually is:
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
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over complex
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capital cost intensive-pipework overdesigned
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modelled poorly in terms of heat exchangers
Network Redesigned Using ESDU’s INTEGRITY™
The overall plant design demonstrates improved
operability and is:
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energy efficient
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less complex
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safer to operate and maintain
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cheaper
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modelled realistically in terms of heat exchangers
Future Developments:
- Retrofit
- Batch Processes
”Process Integration will continue to generate valuable cost
- Site analysis
savings by improved heat recovery and water reuse. Perhaps
- Separation scheme synthesis
the most significant feature of the methodology is the insight
- Distillation column thermodynamics
it provides towards inherently more efficient processes. Proc-
- Heat pumping
ess Integration is a tool that incorporates systematic under-
- Dealing with constraints
standing of process thermodynamics to arrive at optimum
process configuration and operating conditions. Because the
A comprehensive training package is available to enable
methodology can be applied across a whole site, it also
INTEGRITY™ users to achieve maximum benefit in apply-
eliminates the pitfall of designing individual operations that
ing the program to their design projects.
are very efficient, but result collectively in less than optimum
site performance.”
There are other ESDU Process Integration Data Items
on application to utilities, CHP and heat pumps, and
process change and batch processes. Like all ESDU data,
--Harry Cripps,
HRC Consultants, Ltd.
these are now available to subscribers via the Internet or
CD-ROM for stand-alone or network delivery.
ESDU’s on-going work in Process Integration Data will encompass other practical aspects
such as retrofit and will include practical case studies developed with the help of industrial
and academic experts.
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An Engineering Perspective
Develop Simple Integration Schemes
Do you want complicated plants or simple plants?
This is the heat integration scheme developed using
standard Pinch Technology.
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
The scheme is not easy to understand and once piping
costs have been taken into account it is expensive in
terms of capital.
ESDU have been involved in the development of procedures which take layout into consideration. Using these
procedures we can develop the scheme shown below.
This system exhibits similar network economics to the first scheme. However, the flowsheet is seen to be much simpler. The results
are savings in capital and a plant that is both
safer and easier to operate.
The tools necessary for the use of the new
procedure are built into the INTEGRITY™
computer program.
Realistic Exchanger Technology
Other programs ask you to specify stream heat transfer coefficients. How do you get
them? Do you guess? Look at past spec. sheets? Use approximate values from tables?
Use any of these approaches and you move away from reality. The analysis you undertake
may involve sophisticated optimization but what does it mean if the exchanger sizes and
costs are inaccurate.
If you want to guess at a heat transfer coefficient you can still do so. However,
INTEGRITY™ incorporates a model which estimates film heat transfer coefficients from
specified pressure drops or specified velocities.
Specify the four key physical properties (heat capacity,
thermal conductivity, viscosity and density) and then
either:
# fixed stream film coefficient
# stream velocity
or
# stream pressure drop
and the program does the rest. If you have specified a
coefficient, it will tell you the stream velocity and pressure drop. Having specified a velocity it will tell you the
coefficient and the pressure drop. For a specified pres-
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sure drop it will indicate the coefficient and velocity.
INTEGRITY™ INTEGRATE SIMPLY
Both tube-side and shell-side models are available. Just specify which side of the
exchanger the fluid flows through.
The exchanger geometry is set up using radio buttons that allow simple and rapid input.
The program output indicates the surface area each stream is expected to flow over. This
information is useful in identifying poor elements in a network design. Other programs
deal with ‘surface contributions’ not physical surface. Information that has little use in
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
guiding network design.
INTEGRITY™ is easy to use
Data input via simple to use tables. Radio buttons used to
specify exchanger geometry and options.
Analysis Options
On execution the user can choice from a list of three analysis
options:
# Point Target
# Range Target
# Problem Decomposition
Point Target
For Point Calculations the user is required to specify a minimum allowable temperature
approach. The minimum allowable temperature approach is the minimum separation
between the hot and cold composite curves. It can represent a constraint upon exchanger
design. However, it sets the heat recovery level for the problem and controls the capital
cost of the heat recovery network. Its primary purpose is therefore to identify the ‘local’
economics of utility need and network capital cost.
On execution the program will then generate the following information:
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Point Targets
Composite Curves
Heat Demand & Supply Curve (also known as Grand Composite Curve)
Driving Force Plot
Area Distributions (exchanger surface in contact with individual streams)
Point Economics
The screen first gives information on
the Pinch location - the point at which
the hot and cold composites make
their close approach. Both hot and cold
stream temperatures at this location are
listed. They normally differ, of course,
by the specified Minimum Allowable Temperature Difference. However, in the
case of a Threshold Problem - one in
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which the close approach is made at one of the temperature extremes - the difference
can be larger when there is either no economic benefit arising from a closer temperature
approach or, it is impossible to actually close up the difference to the specified value.
The hot and cold utility consumption are listed next. These are the minimum required
needs at the specified minimum allowable temperature approach.
The total utility cost is obtained by multiplying the individual (i.e. hot and cold) consumption rates by the number of hours the plant is to operate each year and the unit cost of
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
the utility and subsequently summing the two values.
The number of individual heat exchanger shells and the minimum network area that
have been predicted for the system are displayed. This is the area that would result
from a system employing heat recovery matches that were vertically aligned between the
composite curves. In a system in which both the hot stream population and all the cold
stream population had uniform heat transfer coefficients this alignment would result in
a true estimate of minimum area. In real systems different streams have different coefficients. In this situation it is often advantageous to match coefficients of like magnitude
and exploit larger temperature differences on the matches having the lower overall coefficient. Such alignment gives area savings. However, the cost benefit of reducing the
number of units can lead to the alignment of some matches that give rise to a need
for more area. The net result of these events is that the vertical alignment model yields
predictions that are about ten percent lower than final designs.
The program predicts the number of matches that will be made (matches for heat
recovery plus matches between process and utility streams). The overall minimum is one
less than the summation of the number of streams (process plus utility). Most designs use
one or two extra units (usually utility units). The prediction here is based on applying the
minimum number equation to the population of streams appearing above the Pinch and
to the population appearing below the Pinch and summing the two results.
The capital cost of the heat exchanger network is a function of the number of exchangers
employed, the overall heat transfer surface used and how that surface is distributed
between the exchangers. The program assumes that the minimum area need is evenly
distributed between the predicted number of exchangers.
The predicted capital cost is multiplied by an annualization factor (which is a function of
specified interest rate and plant life) to yield an annual cost of capital.
Having derived an annual cost of capital all cost predictions are now available on an
annual basis. The Total Annual Cost is the sum of the total utility cost and the annualized
capital cost.
Composite Curves
The hot composite shows the heat that has to be rejected from
the process across the temperature range of the process. The cold
composite shows the heat demanded by the process across the
temperature range of the process. These curves are superimposed
on a T-Q plot such that their separation on the T axis equates with
the Minimum Allowable temperature difference.
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Where the curves overlap heat can be transferred between the hot
INTEGRITY™ INTEGRATE SIMPLY
and cold streams without infringing the minimum temperature approach. This overlap
shows the amount of heat that can be recovered within the process.
The hot end overshoot shows the hot utility demand being made by the process (given
the specified minimum temperature approach).
The cold end overshoot shows the cold utility demand being made by the process.
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The point of close approach is the Pinch Point.
Every feature of these curves can be related to specific aspects of the process. The points
at which the curves change in slope are those at which streams enter and leave the
heat flow picture. They are given by the supply and target temperatures specified for the
individual streams. The slope of each straight section of a ‘curve’ is dependent upon the
streams present across the temperature range curved by that section of line. It equates
with the inverse of the sum of the heat capacity flowrates of the streams present.
The user can pull up the process information whilst examining the curves by clicking on
‘View’ button on the top toolbar and then accessing the ‘Load Table’.
It is possible to engineer the shape of the individual composite curves by changing
the process specification (supply and target temperatures and heat capacity flowrate).
Beneficial changes are generally those which increase the temperatures of the hot streams
and reduce the temperatures of the cold streams.
Hard copy of the curves can be obtained by ‘right clicking’ at a point on the figure and
then selecting ‘print’.
Heat Demand and Supply Diagram
The Heat Demand and Supply Diagram has also been called the
Grand Composite Curve. We have used the name provided
by the originators of the Diagram (Umeda and co-workers at
Chiyoda).
The program predicts the minimum utility needs. This utility
does not necessarily have to be provided at the temperature
extremes of the process. There are occasions in which heat
recovery can be used at these extremes. Th Heat Supply and
Demand Diagram shows the local demand for utility (hot utility
above the Pinch point and cold utility below the Pinch point)
across the full temperature span of the process.
The temperature axis refers to ‘Interval Temperatures’. To relate these to actual process
temperatures the user must add half of the minimum allowable temperature approach
to obtain a hot stream value or subtract half of this approach to obtain a cold stream
value.
Like the composite curves the HDS Diagram is made up of a number of straight line
sections each of which represents a temperature interval of the process. The information
displayed is the heat balance of the interval. Where a line moves to the right the heat
balance indicates a surplus of heat. Where the line moves to the left the heat balance
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yields a heat deficit. When a surplus is available at a higher temperature than a deficit
heat recovery is possible.
The hot utility demand profile (i.e. the relationship between hot utility need and temperature) is given by the lines of deficit not covered by a surplus available at a higher
temperature level.
The cold utility demand profile is given by the lines of surplus that do not cover the
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deficits available at lower temperature levels.
These profiles are used to select the better utility levels for the process. For instance,
they are used to identify where low pressure steam can be used and where refrigeration
may be needed.
The user can select utilities (both temperature level and quantity) on the basis of the HDS
Diagram and then incorporate the selection into the stream data (now treating a utility
stream as a new process stream) and, by undertaking a new point calculation, determine
the full economic implications of the selection.
Processes can be modified in order to open up opportunities for using lower cost
utilities (e.g. waste steam from another plant). Again the ‘deficits’ and ‘surpluses’ and
temperature intervals are set by the process data. The Load Table can be superimposed
on the HDS Diagram in order to identify the features of the process that give rise to
features of the HDS Diagram.
Hard copy of the diagram can be obtained by ‘right clicking’ at a point on the figure
and then selecting ‘print’.
Driving Force Plot
This plot presents information on the temperature alignment between the composite
curves.
To obtain the hot stream temperature which aligns with a
given cold stream temperature move vertically from cold
stream value.
To obtain cold stream temperature which aligns with a
given hot stream temperature move horizontally from hot
stream value.
To identify temperature difference compare plot location
with the dotted line.
Uses of Plot:
1. In Problem Decomposition the plot can be used to identify the temperature points at
which streams having large loads and covering large temperature spans can be subdivided
and subsequently ranked for final thermal integration.
2. The suitability of proposed heat recovery matches can be examined. A line representing
a proposed exchanger can be superimposed upon the plot. A large deviation between this
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line and the plot would suggest a wastage of available temperature driving force and a
possible area penalty.
INTEGRITY™ INTEGRATE SIMPLY
3. To structure the heat recovery trains used to pre-heat trains in order to mitigate fouling
(as described in ESDU’s Guide to Crude Oil Fouling).
Range Targets
For Range Calculations the user is required to
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
input initial value, final value and step size for
the allowable temperature approach. The program will then generate the following information:
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To tal Cost Plot
Energy Target Plot
Area Target Plot
Area-Energy Plot
Range Summary
Total Cost Plot >
This plot shows the relationship
between the Total Annual Cost and
the Minimum Allowable Temperature Approach.
< Energy Target Plot
This plot shows the relationships between
hot and cold utility consumption and Minimum Allowable Temperature Approach.
Points at which the slopes of these lines
change are associated with possible
changes in Pinch Point location.
Target Plot Area >
This plot shows the relationship between network
area and Minimum Allowable
Te mperature Approach.
< Area Energy Plot
This plot shows the relationship
between network area and hot
utility consumption.
Range Summary >
Numerical listing of all of information presented in the above plots
is presented in a table accessed via
the ‘Range Summary’ tab.
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Problem Decomposition
Decomposition Analysis is used for Network Design. This is the technique that leads to the
development of simpler networks.
First, the streams are listed in the order in which they appear on the Process Flow
Diagram. The objective here is to make as much use of localized integration as possible.
A boundary is systematically moved through this stream population and a range target
ESDU product release: 2005-02. For current status, contact ESDU. Observe Copyright.
produced for the streams on each side of the boundary. The two resulting ‘zonal’ total
annual cost predictions are then added to determine the total cost of the decomposed
system. the same is done for the zonal hot utility consumption.
The user can then ‘sort’ the results in order of combined
total cost or combined utility consumption.
Comparison can then be made with the total cost (or utility
consumption) of the overall problem. If a decomposed
problem differs little from the overall problem the decomposition is accepted and the attention then directed at
solving two simplified problems.
This procedure can be taken down to individual heat recovery matches.
Once, the benefits of localized integration have been exhausted, the remaining streams
are then ordered in terms of the Ponton-Donaldson Heuristic:
Match the ‘hot’ stream having the highest supply temperature with the
‘cold’ stream having the highest target temperature
and the exercise repeated.
For problems involving just one hot and one cold process stream ‘Range Targeting’ yields
the optimum recovery level.
The data sets for the simplified sub-problems are obtained via the side tree. To ‘exclude’
a stream from the data set left click on stream (to access stream) and then right click
and select ‘exclude’. The process can be reversed by right clicking and selecting ‘include’.
A stream can be deleted altogether by selecting ‘delete’. A stream can be divided into
two parts by selecting ‘duplicate’ and then editing the temperatures (or, in the case of a
stream split the mass flowrates) in the stream property tab.
A duplicated stream appears at the bottom of the stream set.
Stream ordering can be changed by systematically duplicating the stream - knowing that
the new stream will appear at the bottom of the list - and deleting the original stream.
GUIDANCE ON THE USE OF ALL OF THE TECHNIQUES AND TOOLS DESCRIBED CAN
BE FOUND IN DOCUMENTS ACCOMPANYING THE PROGRAM. THESE DOCUMENTS ALSO
DESCRIBE CASE STUDIES.
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