1. Heat and Power Integration CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard Eden Department of Chemical Engineering Auburn University Lecture No. 9 – Heat and Power Integration: Network Design October 28, 2008 Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel

2. Lecture 9 – Objectives  Compute the pinch temperatures  Compute the Maximum Energy Recovery (MER) targets using graphical and/or algebraic methods  Design a simple Heat Exchanger Network (HEN) to meet the MER targets Given data on the hot and cold streams of a process, you should be able to: Last time!

3. Reviewing Simple Example Design a network of steam heaters, water coolers and exchangers for the process streams. Where possible, use exchangers in preference to utilities. Utilities: Steam @ 150 o C, CW @ 25 o C

4. Simple Example - Targets Units:4 Steam:60 kW Cooling water:18 kW Are these numbers optimal??

5. Not to scale!! Reviewing Simple Example

6. Not to scale!! Reviewing Simple Example

7. Q Cmin = 6 kW Q Hmin = 48 kW T Cpinch = 60 T Hpinch = 70 Maximum Energy Recovery (MER) Targets! Reviewing Simple Example

8. Near Optimal Solution

9. Reviewing Simple Example HEN Representation (Grid Diagram)

10. HEN Grid Diagram The pinch divides the HEN into two parts:  the left hand side (above the pinch)  the right hand side (below the pinch) At the pinch, ALL hot streams are hotter than ALL cold streams by  T min.

11. MER Network Design Step 1:MER Targeting Pinch at 90° (Hot) and 80° (Cold) Energy Targets: Total Hot Utilities: 20 kW Total Cold Utilities:60 kW

12. MER Network Design Step 2:Divide the problem at the pinch

13. MER Network Design Step 3:Design hot-end starting at the pinch Pair up exchangers according to CP-constraints. Immediately above the pinch Pair up streams such that: CP HOT  CP COLD (This ensures that T H  T C   T min )  T min

14. MER Network Design Step 3 Cont’d: Complete hot-end design, by ticking-off streams. 90 240 H Add heating utilities as needed (  MER target) Q Hmin = 20 kW 20

15. MER Network Design Step 4:Design cold-end starting at the pinch Pair up exchangers according to CP-constraints. Immediately below the pinch Pair up streams such that: CP HOT  CP COLD (This ensures that T H  T C   T min )  T min

16. MER Network Design Step 4 Cont’d: Complete cold-end design, by ticking-off streams. C Add cooling utilities as needed (  MER target) Q Cmin = 60 kW 3090 60 35 o

17. MER Network Design Completed Design Note that this design meets the MER targets: Q Hmin = 20 kW and Q Cmin = 60 kW

18. Steps in MER Network Design  MER targeting: Define pinch temperatures, Q hmin and Q Cmin  Divide problem at the pinch  Design hot-end, starting at the pinch:Pair up exchangers according to CP-constraints. Immediately above the pinch, pair up streams such that: CP HOT  CP COLD. “Tick off” streams in order to minimize costs. Add heating utilities as needed (up to Q Hmin ). Do not use cold utilities above the pinch.  Design cold-end, starting at the pinch: Pair up exchangers according to CP-constraints. Immediately below the pinch, pair up streams such that: CP HOT  CP COLD. “Tick off” streams in order to minimize costs. Add heating utilities as needed (up to Q Cmin ). Do not use hot utilities below the pinch.

19. Simple Example Revisited Near Optimal Solution

20. Simple Example Revisited Utilities: Steam @ 150 o C, CW @ 25 o C Q Hmin =48 Q Cmin =6 80 o C H 54 C 120 43 o C 6 100 H 8 40

21.  Compute the pinch temperatures  Compute the Maximum Energy Recovery (MER) targets using graphical and/or algebraic methods  Design a simple Heat Exchanger Network (HEN) to meet the MER targets Given data on the hot and cold streams of a process, you should be able to: Last time! Summary – Heat Integration

22. Other Business Homework –SSL: 10.1, 10.2 –Due Tuesday November 4 Next Lecture – November 4 –Mathematical Optimization (SSL pp. 616-643)