introduction to pinch technology
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Introduction to Pinch Technology
Introduction to Pinch TechnologyTopics
• Introduction
• Heating Curves
• Composite Curves
• Pinch Point
• Network Design
• Crude Distillation Check
• Quiz
Introduction to Pinch TechnologyIntroduction
Representation of exchangers and streams
Cold
Hot
H1
H2
H3
C1
C2
C3This diagram suitable
for two streams.For many streams, this diagram
provides a schematic.
Introduction to Pinch TechnologyIntroduction
Exercise
- Two Hot Streams
- Two Cold Streams
- Steam and Cooling Water
- Temperatures and Duties from Table
Stream WCp Tin Tout Q
H1 0.05 315 240 -3.75
H2 0.20 240 140 -20.0
C1 0.075 40 130 +6.75
C2 0.125 130 260 +16.25
Steam 350 350
CW 27 40
W = Mass
Cp = Heat Capacity
CW = Cooling Water
Q = Duty
Introduction to Pinch TechnologyIntroduction
Exercise
For the given Basis, calculate the following:
- How many exchangers are required?
- What size are the exchangers?
- How much steam and cooling water are required?
Introduction to Pinch TechnologyIntroduction
Exercise
Provide a solution using the ““Dumbbell” representation
Steam
C1
C2
H1
H2
CW
Steam Load
= 23 Units
CW Load
= 23.75 Units
350 350
130 40
260 130
40 27
315 240
240 140
What is downside of this scheme?
Formulate another exchanger network.
Introduction to Pinch TechnologyIntroduction
Exercise
Provide an alternate network solution reducing utility load
Steam
C1
C2
H1
H2
CW
350 350
130 40
260 130
40 27
315 240
240 140
Heat Exchanger A B C D
Calculate stream temperatures and duties.......
WCp=0.075
WCp=0.125
WCp=0.050
WCp=0.200
Introduction to Pinch TechnologyIntroduction
Exercise
Provide an alternate network solution reducing utility load
Steam
C1
C2
H1
H2
CW
350 350
130 40
260 130
40 27
315 240
240 140
Heat Exchanger A B C D
WCp=0.075
WCp=0.125
WCp=0.050
WCp=0.200
Duty=xxx
xxx
Duty=xxx
xxx
Duty=xxx
Duty=xxx
Introduction to Pinch TechnologyIntroduction
Exercise
Provide an alternate network solution reducing utility load
Steam
C1
C2
H1
H2
CW
350 350
130 40
260 130
40 27
315 240
240 140
Heat Exchanger A B C D
WCp=0.075
WCp=0.125
WCp=0.050
WCp=0.200
Duty=6.75
206
Duty=3.75
160
Duty=12.50
Duty=13.25
Introduction to Pinch TechnologyIntroduction
Questions
- Will both exchange networks work?
- Which is better?
- Is there a better network?
- How many combinations of exchange are there?
Conclusions
- Is there a need for an early systematic approach
to exchanger network design?
- The answer to a systematic approach is called
PINCH TECHNOLOGY. It will benefit the
process engineer by providing:
Better planning
Targets for the Utilities
Estimate exchanger targets early
Optimized designs
Introduction to Pinch TechnologyIntroduction
PROCESS UNIT OR
COMPLEX
Process Integration
Feed
Heat Reaction
Feed
Power
Energy
Recovery
Products
Products
Products
Cold
Utility
Hot
Utility
Once the basis of design is established, the Process Engineer
must do the engineering to define the structure within the box.
PINCH TECHNOLOGY is one of the modern tools available
for the Process Engineer.
Introduction to Pinch TechnologyHeating Curves
Construction of Heating Curves
- Two Fluids with constant Cp
- Two Fluids with changing Cp
- Two Fluids with hot and cold utilities
- Finding optimum approach of hot and cold curves
Introduction to Pinch TechnologyHeating Curves
Two Fluids with constant Cp
600
500
400
300
200
100
0
0 0.2 0.4 0.6 0.8 1.0
Tem
per
atu
re
Fraction of Thermal Duty
Hot
Cold
Introduction to Pinch TechnologyHeating Curves
Two Fluids with changing Cp
600
500
400
300
200
100
0
0 0.2 0.4 0.6 0.8 1.0
Tem
per
atu
re
Fraction of Thermal Duty
Cold
Hot
Introduction to Pinch TechnologyHeating Curves
Two fluids with hot and cold utilities
600
500
400
300
200
100
0
0
Tem
per
atu
re
Hot
Cold
20 40 60 80 100
Thermal Duty, MMBTU/Hr
What is Hot Utility?
What is Cold Utility?
What is Exchanger
Duty?
What is Minimum
Temperature Approach?
Introduction to Pinch TechnologyHeating Curves
Two fluids with hot and cold utilities with infinite exchange
600
500
400
300
200
100
0
0
Tem
per
atu
re
Hot
Cold
20 40 60 80 100
Thermal Duty, MMBTU/Hr
What is minimum
heating utility?
What is minimum
cooling utility?
What is temperature
approach?
Is this a reasonable
design?
Introduction to Pinch TechnologyHeating Curves
0
200
400
600
800
1000
1200
0 20 40 60 80 100
Utility
Capital
Total
Delta T Minimum (approach)
Find the optimum approach:
Tabulate Utility, Capital & Total Cost vs Approach
Introduction to Pinch TechnologyHeating Curves
Conclusions
- Two Fluid System
Understandable
Simple
Minimum Calculations
- Extend to PINCH TECHNOLOGY
Many Streams
Overlapping Temperature Ranges
Many Utilities (Steam, CW, Air, Fuel Oil & Gas)
Algorithms for Matching Exchangers
Composite Curves
Plot all cooling services as a single composite curve
Plot all heating services as a single composite curve
T
T
T
T
Q Q
Q Q
Hot
Composite
Cold
Composite
Plot the hot composite streams on a Crude Distillation Unit
STREAMS TEMPERATURE, DEG F DUTY, Q
IN OUT MMBTU/HR
Reduced Crude
Gas Oil PA
Diesel PA
Gas Oil Net
Diesel Net
Kerosene Net
Overhead Vapor
665 175
590 440
530 380
570 120
510 120
400 100
285 140
167.6
40.0
60.0
27.0
22.5
29.1
186.7
Assumptions: Specific Heat constant from inlet to outlet temperature.
Step One: Line up intervals from lowest to highest.
100, 120, 140, 175, 285, 380, 400, 440, 510, 530, 570, 590, 665
Step Two: Determine which intervals are common to which streams.
Step Three: Determine the mean specific heat for each stream.
Step Three: Determine duty associated with each interval.
Step Four: Plot the temperature vs. duty composite curve.
Introduction to Pinch TechnologyComposite Curves
Reduced Crude
Gas Oil PA
Diesel PA
Gas Oil Net
Diesel Net
Kerosene Net
Overhead Vapor
100 120 140 175 285 380 400 440 510 530 570 590
120 140 175 285 380 400 440 510 530 570 590 665
38 32 7 14 24 7 14 7 26
19 5 11 5
8 16 28 8
1 2 7 6 1 2 4 1 2
1 2 7 6 1 2 4
2 2 4 11 10 2
45 142
(WxCp)
0.342
0.267
0.400
0.060
0.058
0.097
1.288
Total 2 4 53 205 54 19 34 79 21 27 12 26
Cumulative 2 6 59 264 318 337 371 450 471 498 510 536
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
Te
mp
era
ture
, D
eg
F
Duty, MMBTU/HR
Hot Composite Curve
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Tem
per
atu
re
Thermal Duty
Hot
Composite
Cold
Composite
Practical use of composite curves
Minimum Delta T or Pinch
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Tem
per
atu
re
Thermal Duty
Hot
Composite
Cold
Composite
Practical use of composite curves
Hot Utility Target
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Tem
per
atu
re
Thermal Duty
Hot
Composite
Cold
Composite
Practical use of composite curves
Cold Utility Target
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Tem
per
atu
re
Thermal Duty
Hot
Composite
Cold
Composite
Practical use of composite curves
Exchange between Hot and Cold Streams
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120 140
Tem
per
atu
re
Thermal Duty
Hot
Composite
Practical use of composite curves
The cold composite can be drawn at any location along the
Q axis as long as T and slopes are maintained. What changes?
Introduction to Pinch TechnologyComposite Curves
Introduction to Pinch TechnologyComposite Curves
0
100
200
300
400
500
600
0 20 40 60 80 100 120 140
Tem
per
atu
re
Thermal Duty
Hot
Composite
Practical use of composite curves
The cold composite can be drawn at any location along the
Q axis as long as T and slopes are maintained. What changes?
Note:The change in the Pinch value is proportional to the change in total utility load.
Introduction to Pinch TechnologyPinch Point
0
200
400
600
800
1000
1200
0 20 40 60 80 100
Utility
Capital
Total
Delta T Minimum
Find the optimum “Delta T Minimum”
Tabulate Utility, Capital & Total Cost vs Delta T Minimum
Pinch Point
Introduction to Pinch TechnologyPinch Point
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Tem
per
atu
re
Thermal Duty
Hot
Composite
Cold
Composite
Practical use of composite curves
Once pinch is set, optimum exchange layout must take
advantage of maximum temperature driving force.
Introduction to Pinch TechnologyPinch Point
Rules to maximize thermal driving force at desired PINCH POINT
•Maintain vertical driving force with exchanger selections
•Select matches with exchangers 100% above pinch
•Select matches with exchangers 100% below pinch
•Do not use cooling utility above pinch
•Do not use heating utility below pinch
Introduction to Pinch TechnologyPinch Point
Rules of Thumb for various processes
- Refrigeration 10 deg F Pinch
- Petrochemical 30 deg F Pinch
- Petroleum 50 deg F Pinch
- High Pressure Units 100 deg F Pinch
Remember once the Pinch is set
- Hot Utility is fixed
- Cold Utility is fixed
Remember exchanger constraints
- Some exchanger configurations are undesirable
- Constraints may prevent attaining desired Pinch
Introduction to Pinch TechnologyNetwork Design
Summary:
- Generate composite curves
Stream data
Temperature data
- Select optimum Pinch Point
Capital costs
Utility costs
- Rules for exchanger selection
No heat transfer across the Pinch Point
Start at Pinch Point and work outward(above & below)
Maintain maximum temperature driving force
Never let exchanger approach drop below Pinch Point
Introduction to Pinch TechnologyNetwork Design
Software
- Is there software to help the Process Engineer?
Linhoff March
Advent
Hysim/Sim Sci
Spreadsheets
- Can software make the exchanger matches?
Yes, as good as the algorithms
Do not underestimate the human interface
- Let us go through with an example
Introduction to Pinch TechnologyNetwork Design
Example
Start the grid by showing all the hot streams(requiring
cooling) to go from left to right and the cold streams
(requiring heating) to go from right to left.
Stream Type W x Cp TempIn TempOut
Cold 2.0 20 135
Hot 3.0 170 60
Cold 4.0 80 140
Hot 1.5 150 30
Plot the composites with a Pinch Point of 10 degrees.
Introduction to Pinch TechnologyNetwork Design
0
20
40
60
80
100
120
140
160
180
0 200 400 600
Tem
per
atu
re
Thermal Duty
Example
Heating Utility = 20
Cooling Utility = 60
Pinch = 10
Introduction to Pinch TechnologyNetwork Design
Example
Layout streams in a grid with the center line at the
Pinch temperatures.
170 90 90 60
150 90 90 30
135 80 80 20
140 80
W x Cp Duty
above below
3.0 240 90
1.5 90 90
2.0 110 120
4.0 240 -
(2)
(4)
(1)
(3)
Introduction to Pinch TechnologyNetwork Design
Example
Start matching exchanger above the Pinch
170 90
150 90
135 80
140 80
W x Cp Duty
above
3.0 240
1.5 90
2.0 110
4.0 240
(2)
(4)
(1)
(3)
170 - 90
140 - 80
30 10
150 - 90
125 - 80
25 10
125 - 135
Q = 240 Q = 90
Q = 20
Hot Utility
Introduction to Pinch TechnologyNetwork Design
Example
Match exchangers below the Pinch
90 60
90 30
80 20
W x Cp Duty
below
3.0 90
1.5 90
2.0 120
(2)
(4)
(1)
(3)
90 - 60
80 - 35
10 25
90 - 70
35 - 20
55 50
70 - 30
Q = 60
Q = 90 Q = 30
Cooling Utility
Introduction to Pinch TechnologyCrude Distillation Unit Design Check
The hot composite streams for the Crude Distillation Unit have
been plotted. Now plot the cold composite streams. Use the exiting
heater duty as the hot utility. What is the resultant Pinch Point?
IN OUT MMBTU/HR
STREAMS TEMPERATURE, DEG F DUTY, Q
Crude to Desalter
Crude to Heater
Crude to Flash Zone
Debut Reboiler
60 260
250 449
449 705
374 375
126.2
152.7
273.7
20.0
Introduction to Pinch TechnologyCrude Distillation Unit Design Check
Crude to Fl Zone
Crude to Heater
Crude to Desalter
Debut Reboiler
705 449 375 374 260 250
449 375 374 260 250 60(WxCp)
1.069
0.767
0.631
20.0
Total 274 57 21 87 14 120
Cumulative (536+274 = 810) 536 479 458 371 357 237
274
57 1 87 8
6 120
20
Introduction to Pinch Technology
Crude Distillation Unit Design Check
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
Te
mp
era
ture
, D
eg
F
Duty, MMBTU/HR
Hot Composite Curve
Introduction to Pinch Technology
Crude Distillation Unit Design Check
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
Te
mp
era
ture
, D
eg
F
Duty, MMBTU/HR
Composite Curves
Introduction to Pinch TechnologyQuiz
1. Based on the individual streams below, calculate the heat duty for the hot
composite curve in the 180-150 deg range.
Stream Q, MMBTU/H Tin Tout
1 20.0 200 100
2 4.5 180 150
3 12.0 160 130
a. 4.5 MMBTU/H
b. 22.5 MMBTU/H
c. 14.5 MMBTU/H
2. The complete composite curve for the streams in Problem 1 would consist
of how many separate temperature zones?
a. 5
b. 3
c. 1
3. The Pinch Point is determined as:
a. The point where the heating and cooling curve cross
b. The temperature difference between the two composite curves that
results in the optimum economic cost.
c. The point where the composite curves just touch
Introduction to Pinch TechnologyQuiz
4. The physical significance of the reducing the Delta Tmin is to:
a. Increase the heat exchange surface area
b. Reduce capital cost
c. Decrease the heat exchange surface area
5. When designing an oil processing facility, a recommended target
pinch temperature is:
a. 70 deg F
b. 50 deg F
c. 20 deg F
6. When selecting the streams that should be used to exchange heat, which
rule of network design applies?
a. Do not exchange heat across the Pinch Point
b. Minimize vertical temperature driving force
c. Exchanger temperature differentials less than the pinch point
temperature are acceptable
7. Heating and cooling utilities are fixed when the pinch point temperature
is selected.
a. True
b. False
Introduction to Pinch TechnologyQuiz
8. From the composite curves developed for the crude unit design, what
is the value of the pinch point temperature?
a. 200 deg F
b. 136 deg F
c. 155 deg F
9. If the cold composite curve developed for the crude unit design is repositioned
laterally to the left, what happens to the heating utility.
a. Increases
b. No change
c. Decreases
10. Pinch technology can be used to help and aid with the process flow scheme
selection.
a. True
b. False
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