#### Transcript PPT - Auburn University

Heat and Power Integration CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard Eden Department of Chemical Engineering Auburn University Lecture No. 10 – Heat and Power Integration: Network Design November 6, 2012 Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel Lecture 9 – Objectives Given data on the hot and cold streams of a process, you should be able to: Compute the pinch temperatures Last time! Compute the Maximum Energy Recovery (MER) targets using graphical and/or algebraic methods Last time! Design a simple Heat Exchanger Network (HEN) to meet the MER targets Reviewing Simple Example 30° 60° 120° 100° ΔH=160 ΔH=162 180° 80° ΔH=100 Utilities: Steam @ 150 oC, CW @ 25oC Stream TS (oC) TT (oC) H1 H2 C1 C2 180 130 60 30 80 40 100 120 CP H o (kW) (kW/ C) 100 1.0 180 2.0 160 4.0 162 1.8 130° 40° ΔH=180 Design a network of steam heaters, water coolers and exchangers for the process streams. Where possible, use exchangers in preference to utilities. Simple Example - Targets 40° 100° ΔH=18 ΔH=60 30° 60° 120° 130° ΔH=162 180° 80° ΔH=100 Units: Steam: Cooling water: 4 60 kW 18 kW Are these numbers optimal?? Reviewing Simple Example 30° 60° 120° 100° ΔH=160 ΔH=162 180° 80° ΔH=100 130° 40° ΔH=180 T T 1.0 1.0 180 180 CP = CP = H=50 130 H=150 C C P = 2. 0 130 =3 P .0 H=150 P = H=80 C Not to scale!! 2. 0 80 80 40 H=50 40 H Not to scale!! H=80 H Reviewing Simple Example 30° 60° 120° 100° ΔH=160 ΔH=162 180° 80° ΔH=100 130° 40° ΔH=180 T T CP = CP = H=36 100 100 H=232 60 C =5 P .8 H=36 H=232 60 Not to scale!! 1.8 = P 4 .0 H=54 CP = C 30 1. 8 120 1.8 120 30 H Not to scale!! H=54 H Temperature Reviewing Simple Example 200 180 160 140 120 100 80 60 40 20 0 QHmin = 48 kW QCmin = 6 kW Maximum Energy Recovery (MER) Targets! THpinch = 70 TCpinch = 60 0 50 100 150 200 Enthalpy 250 300 350 Reviewing Simple Example Near Optimal Solution H1 H2 80oC 180oC 130oC 100oC 120oC 40oC C 7 60oC H 49 111 100 30oC 62 60° C2 100° ΔH=49 80° 30° C1 120° ΔH=62 ΔH=100 180° 40° ΔH=7 ΔH=111 Reviewing Simple Example HEN Representation (Grid Diagram) 180 C 80oC 130oC 40oC o H1 H2 100oC o 120 C C 7 60oC H 49 111 100 30oC 62 C1 C2 HEN Grid Diagram Thot H1 H2 H Thot Thot Tcold Tcold Tcold Tcold C C1 C2 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. MER Network Design CP 170oC 60oC 3.0 150oC 30oC 1.5 H1 H2 135oC 20oC 140oC 80oC C1 2.0 C2 4.0 Step 1: MER Targeting Pinch at 90° (Hot) and 80° (Cold) Energy Targets: Total Hot Utilities: Total Cold Utilities: 20 kW 60 kW MER Network Design Step 2: Divide the problem at the pinch CP 170oC H1 o H2 150 C 135oC 140oC 90oC 90oC 60oC 3.0 90oC 90oC 30oC 1.5 80oC 80oC 20oC 80oC C2 C1 2.0 4.0 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: CPHOT CPCOLD (This ensures that TH TC Tmin) CP H1 3.0 H2 1.5 C1 2.0 C2 4.0 Meets Tmin Violates Tminconstraint constraint Tmin MER Network Design Step 3 Cont’d: Complete hot-end design, by ticking-off streams. CP H1 QHmin = 20 kW H2 170o 150o 90 3.0 90o 135o 140o H 20 o 80o 90 80o 1.5 C1 2.0 C2 4.0 240 Add heating utilities as needed (MER target) 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: CPHOT CPCOLD (This ensures that TH TC Tmin) CP H1 3.0 H2 1.5 C1 2.0 Violates Meets TT constraint constraint minmin Tmin MER Network Design Step 4 Cont’d: Complete cold-end design, by ticking-off streams. CP H1 H2 90o 60o 90o C 60 80o 35o 90 30o 20o C1 3.0 1.5 QCmin = 60 kW 2.0 30 Add cooling utilities as needed (MER target) MER Network Design Completed Design CP H1 H2 170o 150 90o o 135o H 140o 60o 90o 20 80o 125o 90 30o 70o C 60 20o 35o 90 30 80o 3.0 1.5 C1 2.0 C2 4.0 240 Note that this design meets the MER targets: QHmin = 20 kW and QCmin = 60 kW 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. Simple Example Revisited Near Optimal Solution H1 H2 80oC 180oC 130oC 100oC 120oC 40oC C 7 60oC H 49 111 100 30oC 62 60° C2 100° ΔH=49 80° 30° C1 120° ΔH=62 ΔH=100 180° 40° ΔH=7 ΔH=111 Simple Example Revisited Utilities: Steam @ 150 oC, CW @ 25oC Stream TS (oC) TT (oC) H1 H2 C1 C2 180 130 60 30 80 40 100 120 H1 CP H o (kW) (kW/ C) 100 1.0 180 2.0 160 4.0 162 1.8 H2 180oC 80oC 130oC 40oC 100oC 120oC C 7 60oC H 49 111 100 30oC C1 C2 62 CP H1 QHmin=48 H2 180oC 80oC 130oC 100oC 120oC 40 80oC 70oC 43oC 60 C H H 8 120 60oC 100 54 40 C C o 6 o 1.0 2.0 QCmin=6 o 60 C 30oC C1 4.0 C2 1.8 Summary – Heat Integration Given data on the hot and cold streams of a process, you should be able to: Compute the pinch temperatures Last time! Compute the Maximum Energy Recovery (MER) targets using graphical and/or algebraic methods Last time! Design a simple Heat Exchanger Network (HEN) to meet the MER targets 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