8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
1/46
Smith: Chemical Process Design and Integration (Chapters 16,18)Kemp: Pinch Analysis and Process Integration (Chapter 9)
Process Integrationfor Efficient Use of Energy
Cheng-Liang ChenP SELABORATORY
Department of Chemical EngineeringNational TAIWAN University
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
2/46
Chen CL 1
Outline
Systematic Approach for Chemical Process Design
How do we go about the design of a chemical process? What Is Process Integration?Onion model for process integration
Pinch Analysis: Targeting Heat Recovery in Processes
The Pinch Design Method for Heat Recovery Systems
A Pinch Study Performed on A Major Operating Plant
Utility Selection for Individual Processes
Putting It into Practice
Concluding Remarks
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
3/46
Chen CL 2
Heat Exchanger Network Design:The Pinch Design Method
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
4/46
Chen CL 3
Design of Individual Processesfor Maximum Energy Recovery
Divide the process at the pinch
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
5/46
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
6/46
Chen CL 5
Design of Individual Processesfor Maximum Energy Recovery
Cross-pinch heat transfer: Actual = Target + XP
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
7/46
Chen CL 6
Design of Individual Processesfor Maximum Energy Recovery
Cold utility above the pinch Hot utility below the pinch
h
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
8/46
Chen CL 7
Design of Individual Processesfor Maximum Energy Recovery
Design RuleDo Not Transfer Heat Across the Pinch
Do not use steam below Do not use cooling water above
Do not recover process heat across
Ch CL 8
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
9/46
Chen CL 8
Typical Grid Diagram
Ch CL 9
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
10/46
Chen CL 9
Typical Grid DiagramRules for Construction
Hot streams run left to right
Cold streams run right to left
Hot streams on top; Cold streams on bottom
Hot utility =
H
Cold utility = C
Heat exchanger between streams =
Ch CL 10
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
11/46
Chen CL 10
Where Is The Pinch ?
Chen CL 11
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
12/46
Chen CL 11
Pinch Is Easily Shown
Chen CL 12
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
13/46
Chen CL 12
Separate Above/Below-Pinch Regions
Chen CL 13
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
14/46
Chen CL 13
Number of Heat Exchanger Units
Graph any collection of points in which some pairs of points are
connected by lines
Path a sequence of distinct lines which are connected to eachother
Chen CL 14
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
15/46
Chen CL 14
Number of Heat Exchanger Units A graph forms a single component if any two points are joined by
a path Loop a path which begins and ends at the same point (CGDHC)
If two loops have a line in common, they can be linked to forma third loop by deleting the common line (BGCEB + CGDHC BGDHCEB)
The number of independent loops for a graph:
N UNITS = S + L C
N UNITS = # of matches or units (lines in graph theory)S = # of streams including utilities (points in a graph)L = # of independent loopsC = # of components
A single component and loop-free: N UNITS = S 1
Chen CL 15
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
16/46
Chen CL 15
Number of Heat Exchanger Units
If the problem has a pinch:
N UNITS = ( S above pinch 1) (S below pinch 1)
To target the number of units for pinched problems, the streams
above and below the pinch must be counted separately(N UNITS = (5 1) + (4 1) = 7 )
Chen CL 16
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
17/46
Chen CL 16
The Pinch Design Method
Stream Type Supply Temp. Target Temp. H Heat Capacity RateT S (oC ) T T (oC ) (MW ) mC p(MW/ o C )
1. Reactor 1 feed Cold 20 180 +32 .0 0.202. Reactor 1 prod Hot 250 40 31.5 0.153. Reactor 2 feed Cold 140 230 +27 .0 0.304. Reactor 2 prod Hot 200 80 30.0 0.25
Chen CL 17
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
18/46
Chen CL 17
The Pinch Design MethodKnown
No exchanger should have a temp diff. smaller than T min No heat transfer across the pinch by
process-to-process heat transfer inappropriate use of utilities
Compositecurves:
Chen CL 18
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
19/46
Chen CL 18
The Pinch Design MethodStart at the Pinch
( T min exists between all hot/cold streams, the most constrained region )
Chen CL 19
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
20/46
Chen CL 19
The Pinch Design MethodDivide at the pinch
Chen CL 20
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
21/46
Chen CL 20
The Pinch Design MethodCP Inequality for Individual Matches
Above Pinch: if CPH > CPC infeasible!
T h = 162 o (suppose) H h = 0 .25(162 150)
= 3 MWT c = 140 +
3 MW0 .2
MW/o
C= 155 oC T min > T h T c
= 162 155= 7 o C
Chen CL 21
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
22/46
Chen CL 21
The Pinch Design MethodCP Inequality for Individual Matches
Above Pinch: if CPH CPC feasible
T h = 162 o (suppose) H h = 0 .25(162 150)
= 3 MWT c = 140 +
3 MW0 .3
MW/o
C= 150 oC T min < T h T c
= 162 150= 12 oC
Chen CL 22
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
23/46
Chen CL 22
The Pinch Design MethodCP Inequality for Individual Matches
Below Pinch: if CPH < CPC infeasible!
T c = 125 o (suppose) H c = 0 .2(140 120)
= 3 MWT h = 150
3 MW. 15
MW/o
C= 130 oC T min > T h T c
= 130 125= 5 o C
Chen CL 23
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
24/46
The Pinch Design MethodCP Inequality for Individual Matches
Below Pinch: if CPH CPC feasible
T c = 125 o (suppose) H c = 0 .2(140 120)
= 3 MWT h = 150
3 MW. 25
MW/o
C= 138 oC T min < T h T c
= 138 125= 13 oC
Chen CL 24
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
25/46
The Pinch Design MethodCP Inequalities: Summary
for temperature differences to increase moving away from the pinch
Above Pinch: CPH CPC Below Pinch: CPH CPC
Chen CL 25
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
26/46
The Pinch Design MethodThe CP Table
Cold utility must not be used above the pinch hot streams must be cooled to pinch temp. by recovery
hot utility can be used on cold streams above the pinch
Chen CL 26
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
27/46
The Pinch Design MethodThe Tick-Off Heuristic (above pinch)
Now we have identied feasible matches How big should we make them ?
Chen CL 27
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
28/46
The Pinch Design MethodThe Tick-Off Heuristic (above pinch)
Maximize loads to tick off streams to keep capital costs down
Chen CL 28
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
29/46
The Pinch Design MethodThe Tick-Off Heuristic (above pinch)
Then ll in the rest
Chen CL 29
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
30/46
The Pinch Design MethodThe Tick-Off Heuristic (above pinch)
Then ll in the rest
Chen CL 30
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
31/46
The Pinch Design MethodThe Tick-Off Heuristic (below pinch)
Maximize loads to tick off streams to keep capital costs down
Chen CL 31
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
32/46
The Pinch Design MethodThe Tick-Off Heuristic (below pinch)
Maximize loads to tick off streams to keep capital costs down
Chen CL 32
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
33/46
The Pinch Design MethodThe Tick-Off Heuristic (below pinch)
Then ll in the rest
Chen CL 33
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
34/46
The Pinch Design MethodThe Tick-Off Heuristic (below pinch)
Then ll in the rest
Chen CL 34
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
35/46
The Pinch Design MethodThe Tick-Off Heuristic (below pinch)
Note: one match violates CP rulesBut, it is away from the pinch and therefore feasible
Chen CL 35
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
36/46
The Pinch Design MethodThe Tick-Off Heuristic: Summary
To tick off a stream, individual units are made as large as possible the smaller of the two heat duties on the streams being matched
Chen CL 36
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
37/46
The Pinch Design MethodThe Completed Design
Chen CL 37
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
38/46
The Pinch Design Method: Summary
Divide the problem at the pinch into separate problems
Design separate problems, started at the pinch, moving away
Temperature feasibility requires constraints on CP values to besatised for matches between streams at the pinch
Loads on individual units are determined using the kick-off heuristicto minimize # of units
Away from the pinch: more freedom, use judgment and processknowledge
Chen CL 38
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
39/46
Stream Splitting: # of Streams
Cold utility must not be usedabove the pinch All hot streams must be cooled to
pinch temperature by heat recovery
Splitting cold streamsAbove Pinch: S H S C
Chen CL 39
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
40/46
Stream Splitting: # of Streams
Hot utility must not be usedbelow the pinch All cold streams must be heated to
pinch temperature by heat recovery
Splitting hot streamsBelow Pinch: S H S C
Chen CL 40
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
41/46
Stream Splitting: CP Inequality
Above Pinch: CPH CPC Hot stream with larger CP values Split into smaller parallel
hot streams(opt ow rates ?)
Chen CL 41
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
42/46
Stream Splitting: CP Inequality
Below Pinch: CPH CPC Cold stream with larger CP values Split into smaller parallel
cold streams(opt ow rates ?)
Chen CL 42
l l h
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
43/46
Stream-Splitting AlgorithmsAbove the Pinch
Chen CL 43
S S li i l i h
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
44/46
Stream-Splitting AlgorithmsBelow the Pinch
Chen CL 44
D i f I di id l P
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
45/46
Design of Individual Processesfor Maximum Energy Recovery
Pinch Design RuleDo Not Transfer Heat Across the Pinch
Divide at the PINCH
Start at the PINCH and move away
Observe the PINCH rules:
Do not use steam below Do not use cooling water above Do not recover process heat across
Chen CL 45
8/12/2019 Process Integration for Efficient Use of Energyon for Efficient Use of Energy
46/46
Thank You for Your Attention
Questions Are Welcome