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

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 § 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 Integration − Design T. Gundersen Heat 34

Rules for Pinch Exchangers Above Pinch Below Pinch Process, Energy and System Bring Hot Streams to Pinch Bring Cold Streams to Pinch without External Cooling without External Heating T T Δ T min Δ T min Q Q mCp Cj ≥ mCp Hi mCp Hi ≥ mCp Cj n C ≥ n H n H ≥ n C Split Streams ? Split Streams ? Heat Integration − Design T. Gundersen Heat 35

WS-6: Network Design Process, Energy and System Stream T s T t mCp Δ Q kW/°C kW °C °C Specification: Δ T min = 10°C H1 140 40 40 4000 H2 180 50 30 3900 C1 90 120 90 2700 Given: C2 50 200 20 3000 Q H,min = 900 kW Q C,min = 3100 kW Steam 230°C (condensing) T Pinch = 100/90ºC Cooling Water 15C à 25°C Find: The Heat Exchanger Network that meets Targets Heat Integration − Design T. Gundersen Heat 36

WS-6: Network Design Pinch 100°C mCp Process, Energy and System 140° 40° 40 H1 180° 50° 30 H2 90° 120° 90 C1 50° 200° 20 C2 90°C Heat Integration − Design T. Gundersen Heat 37

Applied to the Example Pinch Process, Energy and System mCp 180° (kW/°C) 270° 235.6° 160° 180° 18.0 H1 3 2 Ca 360 kW 220° 60° 180° 80° 22.0 1 H2 4 Cb 440 kW 50° 210° 160° 20.0 2 4 C1 2200 kW 1000 kW 160° 210° 190° 177.6° H 3 1 C2 50.0 1000 kW 620 kW 880 kW 160° Heat Integration − Design T. Gundersen Heat 38

Alternative Network Pinch mCp Process, Energy and System 180° (kW/°C) 270° 160° 180° 18.0 H1 2 Ca 360 kW 220° 60° 180° 80° 22.0 1 H2 4 Cb 440 kW 50° 210° 160° 20.0 H 4 C1 2200 kW 1000 kW 2 222.3° (26) 160° 210° 1620 kW C2 50.0 (24) 196.7° 1 160° 880 kW Heat Integration − Design T. Gundersen Heat 39

Phase 4: Optimization • Basis (from Phase 2 and 3): Process, Energy and System § Network that achieves Maximum Energy Recovery (“MER”) for a given Δ T min § Target for the fewest number of Units ( U min ) and normally U network > U min (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 Integration − Design T. Gundersen Heat 40

Optimization of Stream Splits 270° Process, Energy and System 180° H1 2 220° 180° 1 H2 T 1 2 mCp 1 160° 210° 1620 kW C2 mCp 2 1 T 2 880 kW mCp 1 and mCp 2 affect T 1 and T 2 that in turn affect Areas A 1 and A 2 and thus the Investments Heat Integration − Design T. Gundersen Heat 41

Optimization of Loops Pinch 180° 270° Process, Energy and System 160° T 1 H1 3 2 Ca 360 kW 220° 60° T 2 1 H2 4 Cb 440 kW 50° 210° T 3 2 4 C1 2200 + X 1000 - X 160° 210° T 4 H 3 1 C2 880 ≥ X ≥ - 620 620 + X 880 - X 1000 kW Number of independent Loops Example: from Euler: L = U - ( N - 1) L = 7 - 5 = 2 Loops are primarily used to remove small Units Heat Integration − Design T. Gundersen Heat 42

Optimization of Paths Pinch 186.7° 270° 160° 180° Process, Energy and System H1 3 2 Ca 360 kW 220° 60° 80° H2 4 Cb 440 kW + Y 50° 210° 204° 2 4 C1 3080 kW 120 kW - Y + Y 210° 190° H 3 C2 1500 ≥ Y ≥ - 120 160° 1000 kW 1500 kW + Y - Y Paths are primarily used to restore Driving Forces, secondary to remove small Heat Exchangers Heat Integration − Design T. Gundersen Heat 43

A very simple Network Process, Energy and System 270° 160° 180° H1 3 Ca 360 kW 220° 60° 74.5° H2 4 Cb 320 kW Δ T =10° 50° 210° 4 C1 3200 kW 160° 210° 192.4° H 3 C2 880 kW 1620 kW U = U min = 5 and Q H = 880 < 1000 = Q H,min Heat Integration − Design T. Gundersen Heat 44

Process with Heat Integration 192.4° 160° Process, Energy and System HP Compressor CW 130° Condenser 180° CW 210° Distillation Reactor Column 270° 160° 210° HP CW 60° Reboiler 220° 74.5° Product Feed 50° Heat Integration − Design T. Gundersen Heat 45

Number of Units and Independent Loops Pinch 180° 360 270° 160° H1 3 2 Ca Process, Energy and System 220° 60° 1 4 H2 Cb 440 50° 210° 2 4 C1 1000 2200 160° 210° H 3 1 C2 620 1000 880 L = U network − U min = 7 − 5 = 2 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) Heat Integration − Design T. Gundersen Heat 46

Example with Loops and Paths Pinch Process, Energy and System mCp 180° (kW/°C) 270° 160° 207.8° 180° 18.0 H1 3 2 Ca 360 kW 220° 60° 180° 80° 22.0 1 H2 4 Cb 440 kW 50° 210° 185° 160° 20.0 2 4 C1 HP 2200 kW 500 kW 500 kW 160° 210° 187.6° 177.6° 3 1 C2 50.0 MP 1120 kW 500 kW 880 kW 160° Heat Integration − Design T. Gundersen Heat 47

The Heat Cascade is ST 270ºC - - - - - - - 250ºC basis for another 720 kW H1 + 720 very important Process, Energy and System 230ºC - - - - - - - 210ºC Graphical 500 kW 180 kW C2 - 520 Diagram 200 kW 220ºC - - - - - - - 200ºC 2000 kW 720 kW - 1200 880 kW 800 kW 180ºC - - - - - - - 160ºC 360 kW 400 kW + 400 C1 440 kW 160ºC - - - - - - - 140ºC 1800 kW 1980 kW H2 + 180 70ºC - - - - - - - - 50ºC Notice modified 220 kW + 220 Temperatures and the 60ºC - - - - - - - - 40ºC corresponding Heat Flows Δ T min = 20°C CW Heat Integration − Targeting T. Gundersen Heat 48

Grand Composite Curve ST (or Heat Surplus T' (°C) T 0 ’ = 260 Q H,min = 1000 300 Q H,min + 720 Diagram) Process, Energy and System T 1 ’ = 220 R 1 = 1720 250 - 520 T 2 ’ = 210 R 2 = 1200 200 - 1200 Δ T min = 20°C 150 T 3 ’ = 170 R 3 = 0 Q H,min = 1000 kW + 400 Q C,min = 800 kW 100 T 4 ’ = 150 R 4 = 400 T pinch = 180/160°C + 180 50 T 5 ’ = 60 R 5 = 580 + 220 Q C,min Q (kW) T 6 ’ = 50 Q C,min = 800 CW 0 500 1500 Heat Integration − Targeting T. Gundersen Heat 49

Selection of Utilities Process, Energy and System Utility ID T s T t 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 Heat Integration − Targeting T. Gundersen Heat 50

T' (°C) HP 250 Consumption: Process, Energy and System MP 200 HP: 400 kW Alternative: MP: 600 kW 150 CW: 600 kW HP: 1000 kW LP CW: 800 kW Production: 100 Energy Cost: LP: 200 kW 216,000 $/yr Energy Cost: 50 166,000 $/yr Q (kW) CW 0 0 500 1500 But: Remember Area Cost !! Heat Integration − Targeting T. Gundersen Heat 51

Fewest Number of Units - the Extreme Case Process, Energy and System Process Utility Utility Pinch Pinch Pinch 250° 180° 170° 200° HP MP 270° 160° H1 220° 60° H2 50° 210° C1 160° 210° C2 150° 15° 20° LP CW 180° 160° 150° Heat Integration − Targeting T. Gundersen Heat 52

Summary for the Fewest Number of Units Process, Energy and System • 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 U min 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 Integration − Targeting T. Gundersen Heat 53

WS-2: Heat Integration Specification: Process, Energy and System Stream T s T t mCp Δ H Δ T min = 10°C °C °C kW/°C kW Find: C1 40 300 1.0 260 Q H,min , Q C,min C2 40 300 2.0 520 and H1 320 90 3.0 690 Network Steam 340°C (condensing) Hint: Hot Water 120°C à ≥ 50°C Use Cascade Cooling Water 20°C à ≤ 50°C and Gr.C.C Heat Integration − Introduction T. Gundersen Heat 54

40ºC WS-2: Heat mCp =1.0 320ºC 90ºC R 300ºC Integration mCp =3.0 mCp =2.0 40ºC Balanced Composite Curves T (°C) Process, Energy and System 350 Threshold Problem 300 Do not need Cooling 250 200 Q H,min = 90 kW 150 100 50 Q (kW) 0 0 100 200 300 400 500 600 700 800 900 Grand Composite Curve T’ (°C) 350 ”Pocket” in Grand 300 250 Composite Curve 200 No Need for Steam 150 100 50 Q (kW) 0 0 20 40 60 80 100 120 140 Heat Integration − Introduction T. Gundersen Heat 55

WS-2: Heat Integration & Multiple Utilities α β Process, Energy and System mCp =1.0 40ºC 260 kW E 320ºC R 300ºC 85ºC mCp =3.0 H E 430 kW 90 kW 40ºC Feasible Solution for α and β ?? mCp =2.0 Grand Composite Curve: YES T α T β Must have: T α 50ºC and T β ≥ 95ºC 90ºC è α ≥ 0.963 and β ≥ 1.911 (OK) Heat Integration − Introduction T. Gundersen Heat 56