Pinch technology series Heat Integration An Introduction to Heat Exchanger Network (HEN) Design By: Anwaruddin Hisyam Pinch technology series

Pinch technology series In this lecture we will learn how to set energy recovery targets for a process. Pinch technology series

Pinch technology series Pinch identification Pinch technology series

Pinch technology series Base case Reactor 50 C 160 C 270 C 210 C 220 C 180 C 60 C 130 C 149 C 1620 2640 1980 1220 178 C 880 Pinch technology series

Pinch technology series Data Extraction 178 C 880 1620 160 C 180 C 60 C 2640 130 C 210 C Reactor 270 C 160 C 210 C 149 C 1220 1980 50 C 220 C Pinch technology series

Pinch technology series …..from data extraction Reactor 50 C 160 C 270 C 210 C 220 C 60 C 130 C Pinch technology series

Stream Data (Problem Table) No T source, C T target, C Heat duty, kW CP Type 1 220 60 3520 22 Hot 2 270 160 1980 18 3 50 210 3200 20 Cold 4 2500 CP = Heat duty/ABS(T source – T target) Pinch technology series

Pinch technology series Composite Curve DT min Pinch technology series

Pinch technology series Set DTmin = 20 C Pinch technology series

Pinch technology series Shifted Stream Data Hot - ½DTmin; Cold + ½DTmin No T source, C T target, C Heat duty, kW CP Type 1 210 50 3520 22 Hot 2 260 150 1980 18 3 60 220 3200 20 Cold 4 170 2500 Pinch technology series

Shifted Composite Curve 50 100 150 200 250 300 1000 2000 3000 4000 5000 6000 7000 Heat Duty (kW) Temp interval (K) Pinch technology series

Pinch technology series Cascade Diagram Cold-Hot Stream population Cold Hot 260 220 210 170 150 60 50 720 -720 SURPLUS 700 180 520 DEFICIT 2800 1600 1200 400 800 -400 1800 1980 -180 220 -220 18 20 50 22 Pinch technology series

Heat balance in the interval Hot utility Heat flow 260 220 210 170 150 60 50 720 200 - 1000 - 600 - 420 - 200 -720 520 1200 -400 -180 -220 Cold utility Pinch technology series

The heat flow must NOT be negative Pinch technology series

Pinch technology series Normalization 260 220 210 170 150 60 50 720 200 - 1000 - 600 - 420 - 200 Hot utility -720 520 1200 -400 -180 -220 Cold utility Need additional heat Pinch technology series

Original Grand Composite Curve Unfeasible region Feasible region Pinch technology series

Pinch technology series …finding pinch 260 220 210 170 150 60 50 1000 1720 1200 400 580 800 Hot utility -720 520 -400 -180 -220 Cold utility No heat flow at this point Eureka....! This is the PINCH Pinch technology series

Pinch technology series Grand Composite Curve Qh min Qc min Pinch technology series

Pinch technology series finally…. The PINCH POINT = 170 C which means that Hot stream PINCH = 170+½DTmin = 180 Cold stream PINCH = 170-½DTmin = 160 Pinch technology series

Pinch technology series Heat source and sink Heat source  this part releases heat Heat sink  this part requires heat PINCH Heat Source Heat Sink Pinch technology series

and, how can we design HEN based on the pinch? Pinch technology series

Base case….the existing network 220 60 270 160 210 50 H C 2640 1620 880 1980 1220 Heat recovery = 1980 + 880 = 2860 kW Cold utility = 2640 kW Hot utility = 1220 + 1620 = 2840 kW Pinch technology series

Let’s start from the pinch Pinch technology series

Pinch technology series 220 60 270 160 210 50 180 2200 AT 170 PINCH 360 2640 1000 2500 1640 880 20 18 22 CP BELOW ABOVE Pinch technology series

Pinch technology series Rules…. CP in ≤ CP out Start finding partners for streams OUT (with streams IN, away from pinch, or utility) N stream IN ≤ N stream out If Ns IN > Ns OUT, split stream(s) OUT If CP in > CP out (no match), try to split stream(s) IN Set maximum heat recovery The remaining heat duty is covered by heater or cooler Pinch technology series

Pinch technology series Step 1: Below the PINCH Connect S1(22) and S3(20) CP in < CP out 220 60 270 160 210 50 1 180 2200 √ Pinch technology series

Pinch technology series Step 2: Above the PINCH Connect S2(18) and S4(50) CP in < CP out 220 60 270 160 210 50 1 180 2200 √ 2 1620 Pinch technology series

Pinch technology series Step 3: Above the PINCH Connect S1(22) and S4(50) CP in < CP out 220 60 270 160 210 50 1 180 2200 √ 2 1620 3 880 2500 Pinch technology series

Pinch technology series Step 4: Above the PINCH Install Heater at S3(20) 220 60 270 160 210 50 1 180 2200 √ 2 1620 3 880 2500 H 1000 Pinch technology series

√ √ √ √ √ √ √ All heat requirements have been met !!! Step 5: Below the PINCH Install Cooler at S1(22) and S2(18) 440 880 √ 180 √ 2640 60 C 1 3 220 880 360 1620 √ 180 √ 360 C 160 2 270 1620 1000 √ 160 √ H 2200 50 1 210 1000 2200 160 √ 3 2 160 210 2500 All heat requirements have been met !!! Pinch technology series

…finally… Heat Exchanger Network (HEN) 220 60 270 160 210 50 H 2200 440 1000 1620 880 C 360 Maximum Energy Recovery (MER) = 2200 + 880 + 1620 = 4700 kW Minimum cooling heat duty (Qc min) = 440 + 360 = 800 kW Minimum heating heat duty (Qh min) = 1000 kW Pinch technology series

Then draw the flowsheet… Reactor 50 C 160 C 270 C 210 C 220 C 60 C 130 C 880 1620 2200 440 360 1000 177.6 C 180 C 80 C Pinch technology series

Possible modifications Pinch technology series

Pinch technology series Grand Composite Curve MP steam Heat generation Cooling water Pinch technology series

Pinch technology series Thank you Pinch technology series

Pinch technology series Working Session Pinch technology series

Pinch technology series How will the HEN be….? Feed 2 Feed 1 H= 27 MW H=32 MW H= -31.5 MW H=-30 MW 140 C 250 C 230 C 40 C 180 C 20 C 200 C 80 C Product 2 Product 1 Reactor 1 Reactor 2 Pinch technology series