Heat and Power Integration

1. Heat and Power Integration CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard EdenDepartment of Chemical EngineeringAuburn University Lecture No. 10 – Heat and Power Integration: Network Design November 6, 2012 Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel

2. Lecture 9 – Objectives Given data on the hot and cold streams of a process, you should be able to: Last time!  • 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  Last time!

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

4. Simple Example - Targets Units: 4Steam: 60 kWCooling water: 18 kWAre these numbers optimal??

5. Reviewing Simple Example Not to scale!! Not to scale!!

6. Reviewing Simple Example Not to scale!! Not to scale!!

7. Reviewing Simple Example QHmin = 48 kW QCmin = 6 kW Maximum Energy Recovery (MER) Targets! THpinch = 70 TCpinch = 60

8. Reviewing Simple Example 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 Tmin.

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. Tmin MER Network Design Step 3: Design hot-end starting at the pinchPair up exchangers according to CP-constraints.Immediately above the pinch Pair up streams such that: CPHOT CPCOLD (This ensures that THTCTmin)

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

15. Tmin MER Network Design Step 4: Design cold-end starting at the pinchPair up exchangers according to CP-constraints.Immediately below the pinch Pair up streams such that: CPHOT CPCOLD (This ensures that THTCTmin)

16. C MER Network Design Step 4 Cont’d: Complete cold-end design, by ticking-off streams.   QCmin = 60 kW  60  35o 90 30 Add cooling utilities as needed (MER target)

17. MER Network Design Completed Design Note that this design meets the MER targets: QHmin = 20 kW and QCmin = 60 kW

18. Steps in MER Network Design • MER targeting: Define pinch temperatures, Qhmin and QCmin • 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: CPHOT CPCOLD. “Tick off” streams in order to minimize costs. Add heating utilities as needed (up to QHmin). 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: CPHOT CPCOLD. “Tick off” streams in order to minimize costs. Add heating utilities as needed (up to QCmin). Do not use hot utilities below the pinch.

19. Simple Example Revisited Near Optimal Solution

20. 80oC • C • H • H Simple Example Revisited Utilities: Steam @ 150 oC, CW @ 25oC    43oC  QHmin=48  QCmin=6 6  40 120   8 100 54

21. Summary – Heat Integration Given data on the hot and cold streams of a process, you should be able to: Last time!  • 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  Last time!

22. Other Business • Next Lectures – November 13 & 27 • Class review • Simulation Project Reports • Due Thursday November 29 • Final Exam – December 3 • Ross 136 • 8:00 AM – 10:30 AM