Phase 3: Design Basis (from Phase 2): Process, Energy and System - - PowerPoint PPT Presentation

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Phase 3: Design Basis (from Phase 2): Process, Energy and System - - PowerPoint PPT Presentation

Nov 29, 2023 202 likes •465 views

Phase 3: Design Basis (from Phase 2): Process, Energy and System Decomposition at the Pinch Point(s) Minimum Energy Requirements ( Q H,min , Q C,min ) Fewest Number of Units ( U min , U min,MER ) Pinch Design Method

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SLIDE 1

Phase 3: Design

  • T. Gundersen
  • Basis (from Phase 2):

§ Decomposition at the Pinch Point(s) § Minimum Energy Requirements (QH,min , QC,min) § Fewest Number of Units (Umin , Umin,MER)

  • Pinch Design Method

§ Separate Networks above and below Pinch § Design is started at the Pinch (critical region) § Rules for “Pinch Exchangers” assure that we have sufficient Temperature Driving Forces § Maximize the Duty for each Unit (“Tick-off”)

Heat 34

Process, Energy and System Heat Integration − Design

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SLIDE 2

Rules for Pinch Exchangers

Below Pinch

mCpHi ≥ mCpCj nH ≥ nC Split Streams ? Bring Cold Streams to Pinch without External Heating T Q ΔTmin

Above Pinch

Bring Hot Streams to Pinch without External Cooling mCpCj ≥ mCpHi nC ≥ nH Split Streams ? T Q ΔTmin

  • T. Gundersen

Heat 35

Process, Energy and System Heat Integration − Design

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SLIDE 3

WS-6: Network Design

  • T. Gundersen

Stream Ts Tt mCp ΔQ °C °C kW/°C kW H1 140 40 40 4000 H2 180 50 30 3900 C1 90 120 90 2700 C2 50 200 20 3000 Steam 230°C (condensing) Cooling Water 15C à 25°C Specification: ΔTmin = 10°C Given: QH,min = 900 kW QC,min = 3100 kW TPinch = 100/90ºC

Process, Energy and System

Heat 36

Find: The Heat Exchanger Network that meets Targets

Heat Integration − Design

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SLIDE 4

WS-6: Network Design

  • T. Gundersen

Process, Energy and System

Heat 37

C2

200° 50°

C1

120°

H2

180° 50°

H1

140° 40° 90°

mCp 40 30 90 20

Pinch

100°C 90°C

Heat Integration − Design

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SLIDE 5

Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° 160° Ca

4 4 H 1 1 3 3 2 2

190° 177.6° 1000 kW 1000 kW 620 kW 880 kW Cb 360 kW 440 kW 2200 kW 160° 180° 180° 80° 235.6°

mCp

(kW/°C) 18.0

22.0 20.0 50.0

Applied to the Example

  • T. Gundersen

Heat 38

Process, Energy and System Heat Integration − Design

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SLIDE 6

Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° 160° Ca

4 4 H

196.7° 222.3°

2 2

1620 kW 1000 kW

1 1

880 kW Cb 360 kW 440 kW 2200 kW 160° 180° 180° 80°

mCp

(kW/°C) 18.0

22.0 20.0 50.0

(26) (24)

Alternative Network

  • T. Gundersen

Heat 39

Process, Energy and System Heat Integration − Design

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SLIDE 7

Phase 4: Optimization

  • T. Gundersen
  • Basis (from Phase 2 and 3):

§ Network that achieves Maximum Energy Recovery (“MER”) for a given ΔTmin § Target for the fewest number of Units (Umin) and normally Unetwork > Umin (Optimize?)

  • Degrees of Freedom in the Network:

§ Branch Flowrates in the case of Stream Splits § Heat Load Loops (see later slides) § Heat Load Paths (see later slides)

Heat 40

Process, Energy and System Heat Integration − Design

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SLIDE 8

Optimization of Stream Splits

C2 210° 160° H2 220° H1 270°

T2 2 2

1620 kW

1 1

880 kW 180° 180°

mCp1 mCp2 T1

mCp1 and mCp2 affect T1 and T2 that in turn affect Areas A1 and A2 and thus the Investments

  • T. Gundersen

Heat 41

Process, Energy and System Heat Integration − Design

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SLIDE 9

Optimization of Loops

Number of independent Loops from Euler: L = U - (N - 1) Example: L = 7 - 5 = 2 Loops are primarily used to remove small Units

  • T. Gundersen

Heat 42

Process, Energy and System Heat Integration − Design

Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° Ca

4 4 H 1 1 3 3 2 2

Cb 620 + X 880 - X 2200 + X 1000 - X T1 T2 T3 T4

880 ≥ X ≥ - 620

1000 kW 360 kW 440 kW

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SLIDE 10

Optimization of Paths

Pinch C2 210° 160° C1

210°

50° H2

220°

60° H1 270° 160° Ca

4 4 H 3 3 2 2

Cb 1000 kW + Y 1500 kW

  • Y

120 kW + Y 3080 kW

  • Y

360 kW 440 kW + Y 190°

186.7° 180° 204°

80°

1500 ≥ Y ≥ - 120

Paths are primarily used to restore Driving Forces, secondary to remove small Heat Exchangers

  • T. Gundersen

Heat 43

Process, Energy and System Heat Integration − Design

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SLIDE 11

A very simple Network

U = Umin = 5 and QH = 880 < 1000 = QH,min

C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° Ca

4 4 H

Cb 880 kW

3 3

1620 kW 3200 kW 360 kW 320 kW 192.4° 180° 74.5°

ΔT=10°

  • T. Gundersen

Heat 44

Process, Energy and System Heat Integration − Design

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SLIDE 12

Process with Heat Integration

Product Distillation Column Compressor 210° 160° 130° 220° 160° 270° 60° Feed 50° 210° Reboiler Condenser 74.5° HP CW 180° CW CW HP 192.4° Reactor

  • T. Gundersen

Heat 45

Process, Energy and System Heat Integration − Design

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SLIDE 13

Number of Units and Independent Loops

1 Loop (A) (Total: 1) : 2 Loops (A, B) – Combine (A,B) (Total: 3) 3 Loops (A,B,C) – Combine (A,B), (A,C) & (B,C) (Total: 6)

  • T. Gundersen

Heat 46

Process, Energy and System Heat Integration − Design

Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° Ca

4 4 H 1 1 3 3 2 2

Cb 620 880 2200 1000 1000 360 440

L = Unetwork − Umin = 7 − 5 = 2

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SLIDE 14

Example with Loops and Paths

Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° 160° Ca

4 4

HP

1 1 3 3 2 2

185° 187.6° 500 kW 500 kW 1120 kW 880 kW Cb 360 kW 440 kW 2200 kW 160° 180° 180° 80° 207.8°

mCp

(kW/°C) 18.0

22.0 20.0 50.0 500 kW 177.6°

MP

  • T. Gundersen

Heat 47

Process, Energy and System Heat Integration − Design

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SLIDE 15

The Heat Cascade is basis for another

very important

Graphical Diagram

  • T. Gundersen

Heat 48

Process, Energy and System Heat Integration − Targeting

270ºC - - - - - - - 250ºC 230ºC - - - - - - - 210ºC 220ºC - - - - - - - 200ºC 180ºC - - - - - - - 160ºC 160ºC - - - - - - - 140ºC 70ºC - - - - - - - - 50ºC

H1 H2 CW C1 C2 ST

720 kW 180 kW 720 kW 880 kW 440 kW 1980 kW 500 kW 200 kW 800 kW 1800 kW + 720

  • 520
  • 1200

2000 kW 400 kW + 180 + 220 + 400 60ºC - - - - - - - - 40ºC 360 kW 220 kW

ΔTmin = 20°C

Notice modified Temperatures and the corresponding Heat Flows

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SLIDE 16

T6

’ = 50 QC,min = 800

CW ST

+ 720

  • 520
  • 1200

+ 180 + 220 + 400

T0

’ = 260 QH,min = 1000

T1

’ = 220 R1 = 1720

T2

’ = 210 R2 = 1200

T3

’ = 170 R3 = 0

T4

’ = 150 R4 = 400

T5

’ = 60 R5 = 580

Grand Composite Curve (or Heat Surplus Diagram)

300 250 200 150 100 50 T' (°C) Q (kW) 500 1500

QH,min QC,min ΔTmin = 20°C QH,min = 1000 kW QC,min = 800 kW Tpinch = 180/160°C

  • T. Gundersen

Heat 49

Process, Energy and System Heat Integration − Targeting

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SLIDE 17

Selection of Utilities

Utility ID Ts Tt Price °C °C $/kWyr HP Steam HP 250 250 200 MP Steam MP 200 200 170 LP Steam LP 150 150 140 Cooling Water CW 15 20 20

Optimal Selection of Utility Types / Amounts determined from the Grand Composite Curve

  • T. Gundersen

Heat 50

Process, Energy and System Heat Integration − Targeting

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SLIDE 18
  • T. Gundersen

Heat 51

Process, Energy and System Heat Integration − Targeting

250 200 150 100 50

Q (kW)

500 1500 MP HP LP CW

Consumption: HP: 400 kW MP: 600 kW CW: 600 kW Production: LP: 200 kW Energy Cost: 166,000 $/yr Alternative: HP: 1000 kW CW: 800 kW Energy Cost: 216,000 $/yr

But: Remember Area Cost !!

T' (°C)

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SLIDE 19

Fewest Number of Units

  • the Extreme Case

Process Pinch 180° C2 210° 160° C1 210° 50° H2 220° 60° H1 270° 160° 160° HP 250° MP 180° LP 150° 150° Utility Pinch 200° Utility Pinch 170° CW 15° 20°

  • T. Gundersen

Heat 52

Process, Energy and System Heat Integration − Targeting

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SLIDE 20

Summary for the Fewest Number of Units

  • T. Gundersen
  • The Number of Units depends on:

§ Decomposition or not at the Pinch § Number of Utility Types (HP, MP, LP, CW) § Maximum amount of Intermediate Utilities create additional Utility Pinch Points

  • Some Umin Values for the Example:

§ Only HP and CW without Decomposition: 5 § Only HP and CW with Decomposition: 7 § HP, MP, LP and CW with Decomposition: 14

Heat 53

Process, Energy and System Heat Integration − Targeting

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SLIDE 21

WS-2: Heat Integration

  • T. Gundersen

Stream Ts Tt mCp ΔH °C °C kW/°C kW C1 40 300 1.0 260 C2 40 300 2.0 520 H1 320 90 3.0 690 Steam 340°C (condensing) Hot Water 120°C à ≥ 50°C Cooling Water 20°C à ≤ 50°C Specification: ΔTmin = 10°C Find: QH,min ,QC,min and Network Hint: Use Cascade and Gr.C.C

Heat Integration − Introduction Process, Energy and System

Heat 54

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SLIDE 22

WS-2: Heat Integration

  • T. Gundersen

Heat Integration − Introduction Process, Energy and System

Heat 55

R

mCp=1.0 mCp=2.0 mCp=3.0

40ºC 40ºC 320ºC 300ºC 90ºC

Balanced Composite Curves

50 100 150 200 250 300 350 100 200 300 400 500 600 700 800 900

Q (kW) T (°C) Threshold Problem Do not need Cooling QH,min = 90 kW ”Pocket” in Grand Composite Curve No Need for Steam Grand Composite Curve

50 100 150 200 250 300 350 20 40 60 80 100 120 140

Q (kW) T’ (°C)

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SLIDE 23

WS-2: Heat Integration & Multiple Utilities

  • T. Gundersen

Heat Integration − Introduction Process, Energy and System

Heat 56

R

mCp=3.0 mCp=1.0 40ºC mCp=2.0 40ºC 320ºC 300ºC 90ºC

H E E

90 kW 260 kW 430 kW

α β

Tα Tβ

85ºC

Feasible Solution for α and β ?? Grand Composite Curve: YES Must have: Tα 50ºC and Tβ ≥ 95ºC è α ≥ 0.963 and β ≥ 1.911 (OK)

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SLIDE 24

Summary: Pinch Analysis for

the “Grassroot” Case

  • T. Gundersen
  • Daily used in many Process Industries
  • Simple, Systematic Methods for Design &

Optimization of Heat Exchanger Networks

  • Graphical Diagrams and Representations

§ Composite Curves § Heat Cascade § Grand Composite Curve § Stream Grid for the Design Phase

  • Principle: Targeting before Design

Heat 57

Process, Energy and System Heat Integration − Design