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TEP 4215

E&P/PI

R

S

H

U

- Reactor System (R)
- Endothermic vs. Exothermic Reactions
- Equilibrium vs. Kinetics
- Temperature Dependence of Equilibrium Constants and Reaction Rates (Arrhenius)
- Reactors play a key Role in the Thermal and the Mechanical Energy System of a Plant (or Site)
- Correct Integration of Reactors

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 1

S

Summary for

TEP 4215

E&P/PI

R

S

H

U

- Reactor / Separator Interface (R/S)
- Focus of the Discussion was based on the Definition and Use of the following Terms:
- Degree of Conversion (Extent of Reaction)
- Selectivity
- Yield (Reactor and Process)
- Recycle Rate

Process, Energy and System

FF

RF

P

RX

PX

YR = X · S

BP

RR

YP = X · S · (1 + W)

Summary of Process Integration

T. Gundersen

Sum 2

TEP 4215

E&P/PI

R

S

H

U

- Separation System (S)
- Economical Trade-offs in Distillation Columns
- Operating Cost vs. Investment Cost
- Number of Stages, Reflux and Pressure
- Combinatorial Issues & Heuristic Rules related to the Sequence of Distillation Columns
- Heat Integration Opportunities between Columns (Condenser / Reboiler)
- Briefly about Evaporators
- Multi-effect, Forward/Backward Feed, BPR

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 3

Sequence of Distillation Columns

Problem Definition by Thompson and King, AIChE Jl, 1972:

”Given a mixture of N chemical components that is to be separated into N pure component products by using a selection of M separation methods”

Process, Energy and System

Separation Systems

Sum 4

T. Gundersen

Columns

B

C

D

A

B

C

A

B

C

B

C

D

2 comps. 1 sequence

3 comps. 2 sequences

4 comps. 2x(1+3 comps.)

+ 1x(2+2 comps.)

2x2 + 1 = 5 sequences

5 comps. 2x(1+4 comps.)

+ 2x(2+3 comps.)

2x5 + 2x2 = 14 sequences

6 comps. 2x(1+5 comps.)

+ 2x(2+4 comps.)

+ 1x(3+3 comps.)

2x14 + 2x5 + 2x2 = 42 sequences

A

B

B

C

C

D

C

D

A

B

B

C

A

B

C

D

A

B

C

D

A

B

C

D

A

B

C

D

Process, Energy and System

Separation Systems

T. Gundersen

Sum 5

Sequence of Distillation Columns

Selected Heuristic Rules

H1: Favor Separation of the most Volatile Component

H2: Favor near-Equimolar Separation

H3: Favor Separation of the most Plentiful Component

H4: Favor Simple Separations

<< H5: Delay Separation of Sharp Splits >>

Process, Energy and System

Heuristics cause Conflicts, some can be Quantified, others just ”cast a vote”, their main use is to Eliminate Sequences !!

Separation Systems

T. Gundersen

Sum 6

Comp.NameMole Frac.α=Ki/Kj”CES”

A Propane 0.05

2.00 5.26

B i-Butane 0.15

1.33 8.25

C n-Butane 0.25

2.40 114.50

D i-Pentane 0.20

1.25 13.46

E n-Pentane 0.35

Example – Distillation Sequence

Process, Energy and System

Nadgir & Liu, AIChE Journal, 1983:

f = min (D/B, B/D) Δ = (α – 1)100 CES = f α

Separation Systems

T. Gundersen

Sum 7

TEP 4215

E&P/PI

R

S

H

U

- Heat Recovery System (H)
- Targets for best Performance
- Minimum Energy from the Heat Cascade
- Minimum Energy Cost with Multiple Utilities from the Grand Composite Curve
- Fewest Number of Units from the (N – 1) Rule
- Minimum Area from Spaghetti Design (“Bath”)
- Total Annual Cost vs. ΔTmin
- 3-Way Trade-off (Area, Energy and Units)

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 8

Heat Cascade as Algorithm/Procedure (1)

(0) Given Set of Hot Stream Temperatures: TH , i = 1,nH , Set of Cold Stream Temperatures: TC , j = 1,nC, and Set of mCps, i = 1,nH , j = 1,nC

(1) Calculate Shadow Temperatures from Hot Streams: THS , TH,S=TH−ΔTmin

(2) Calculate Shadow Temperatures from Cold Streams: TCS , TC,S=TC+ΔTmin

(3) Obtain Total Set of Hot Stream Temperatures, THT, by merging and sortingTH and TCSNotice that dim (THT)= nH + nC

(4) Obtain Total Set of Cold Stream Temperatures, TCT, by merging and sortingTC and THSNotice that dim (TCT) = nC + nH

Remove possible Duplicates in THT and TCT. The number of Temperature Intervals is then K = dim (THT) − 1

Temperature Intervals are now obtained by using one Temperature from THT and one from TCT starting at the highest Temperatures

(7) Identify Heat Flows from all the Hot Streams to the respective Temperature Intervals based on mCp values and Interval Temperatures

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 9

Heat Cascade as Algorithm/Procedure (2)

(8) Identify Heat Flows from the respective Temperature Intervals to all the Cold Streams based on mCp values and Interval Temperatures

(9) Calculate the Enthalpy (Heat) Balance (Surplus or Deficit) for each Temperature Interval

(10) Cascade Heat from the first Interval to the second, and from the second to the third Interval. Continue to the end of the Cascade

(11) If all Residuals (i.e. Heat from one Interval to the next) are non-negative (Rk≥ 0), then no External Heating is required, QH,min = 0, and Minimum External Cooling is obtained as the Residual from the last Interval, i.e. QC,min = RK

If at least one Residual is negative, then Minimum External Heating and Cooling are: QH,min = − min (Rk) , k = 1,K-1 , QC,min = RK + QH,min

(13) The Process Pinch is the Interval Temperature with the most negative Residual which has zero heat flow after adding Minimum External Heating to the Cascade

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 10

Example: Stream Data from Assignment 3

Stream Ts(°C) Tt (°C) mCp (kW/°C) ΔH (kW)

H1 170 60 3.0 330

H2 150 30 1.5 180

C1 20 135 2.0 230

C2 80 140 4.0 240

Process, Energy and System

ΔTmin = 10°C

THT = 170, 150, 145, 90, 60, 30

TCT = 160, 140, 135, 80, 50, 20

K = 6 – 1 = 5

Summary of Process Integration

T. Gundersen

Sum 11

Example: Stream Data from Assignment 3

170°C 160°C

60 kW

H1

+ 60

R1=60

150°C 140°C

15 kW

20 kW

+ 2.5

7.5 kW

C2

R2=62.5

145°C 135°C

Process, Energy and System

165 kW

220 kW

- 82.5

82.5 kW

110 kW

R3=−20

H2

90°C 80°C

45 kW

60 kW

+ 75

C1

90 kW

R4=55

60°C 50°C

60 kW

- 15

45 kW

R5=40

30°C 20°C

Summary of Process Integration

T. Gundersen

Sum 12

Vertical Design:

2 −3 and 1 − 4

Criss-Cross Design:

2 −4 and 1 − 3

T(°C)

350

4

3

2

1

300

250

Process, Energy and System

200

Q(kW)

0

500

1000

Explanation: Optimal Distribution of (UΔT) - not only ΔT

Investment Cost

T. Gundersen

Sum 13

TEP 4215

E&P/PI

R

S

H

U

- Heat Recovery System (H)
- Design of Network using PDM
- Decomposition at Pinch (Process and Utility Pinch)
- Start the Design at the Pinch
- Pinch Exchangers and Requirements
- mCp Rules: mCpout≥mCpin
- Population: nout≥nin
- Focus on ΔT, not ΔH
- Tick-off Rule
- Check Design against Targets !!

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 14

TEP 4215

E&P/PI

R

S

H

U

- Heat Recovery System (H)
- Optimization of Heat Exchanger Networks
- Stream Splitting (start with: α/β= mCp1/mCp2)
- Heat Load Loops and Paths
- The HEN Design Process as a “Flow Diagram”
- Retrofit Design of Heat Exchanger Networks
- Targeting for good value of HRAT
- XP Analysis (QP = QPP + QPH + QPC)
- Shifting to reduce XP Heat Transfer
- UA Analysis (existing and new) followed by Loops and Paths for maximum Reuse of existing Units

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 15

Exam 2 June 2008 – Retrofit (60%)

mCp = 50 kW/°C

mCp = 60 kW/°C

Process, Energy and System

mCp = 80 kW/°C

mCp = 40 kW/°C

ΔTmin = 10°C

mCp = 20 kW/°C

Summary of Process Integration

T. Gundersen

Sum 16

Process, Energy and System

Simplified Cascade with

Supply Temperatures only

Summary of Process Integration

T. Gundersen

Sum 17

I

Ca

H2

II

III

III

C1

H

II

C3

C2

I

Cross-Pinch Analysis

Exam 2008

110°

mCp

(kW/°C)

180°

121.67°

4300

50°

[60]

200°

77.5°

70°

110°

[40]

Cb

300

40°

105°

[20]

Process, Energy and System

1300

190°

145°

100°

[80]

3600

3600

60°

130°

[50]

3500

100°

Summary of Process Integration

T. Gundersen

Sum 18

I

Ca

mCp

(kW/°C)

180°

121.67°

50°

[60]

200°

4300-y

145°

190°

[80]

IV

IV

H

3600-y

0 + y

60°

C2

C3

130°

I

[50]

3500

“Shifting”

Exam 2008

TH1

Process, Energy and System

y can be found by ΔTmin requirements y = 1500 kW

Next: What about Investments ??

Summary of Process Integration

T. Gundersen

Sum 19

(kW/°C)

H1

180°

50°

96.67°

155°

IV

I

[60]

Ca

2800

200°

H2

77.5°

70°

110°

[40]

II

Cb

III

300

40°

105°

III

[20]

C1

1300

100°

163.75°

190°

145°

H

IV

II

[80]

2100

3600

1500

60°

C2

C3

130°

I

[50]

3500

Exam 2008

Process, Energy and System

Next: UA Analysis for maximum

Reuse of existing Exchangers

Summary of Process Integration

T. Gundersen

Sum 20

TEP 4215

PI

R

S

H

U

- Separation/Heat Recovery Interface (S/H)
- Columns integrated above/below Pinch
- Condenser above, Reboiler below
- Which Pinch – Columns often create Pinch
- Extended Grand Composite Curve (Andrecovich)
- Distinguish Columns from “Background” Process
- Evaporators and Heat Integration
- The Tool is again the Grand Composite Curve
- Play with Pressure and the Number of Effects

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 21

TEP 4215

PI

R

S

H

U

- Heat Recovery / Utility Interface (H/U)
- Correct Integration of Heat Pumps (open/closed)
- Correct Integration of Turbines (back pressure or extraction vs. condensing turbines)
- Co-production of Heat & Power (cogeneration)
- The quantitative Tool with Information about Load (heat duty) and Level (temperature) is:
- The Grand Composite Curve
- Modified Temperatures are important !!

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 22

TEP 4215

PI

R

S

H

U

- Utility System (U)
- Not treated in much Detail in this Course
- Topics could (or should?) have been:
- Design of Steam Systems (turbines, boilers, deaerators, etc.)
- Design of fired Heaters (Furnaces) with optimal preheat of Combustion Air
- Design of Refrigeration Cycles including Integration with the Process (“economizers”)
- Etc., etc.

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 23

TEP 4215

PI

R

S

H

U

- Other Topics
- Optimization: Only Demo with Examples from Heat Recovery using Math Programming
- Forbidden Matches & Extended Cascade is relevant
- Operational Aspects (especially related to Flexibility and Controllability)
- The Importance of Topology (Structure)
- Extensions of the Pinch Principle
- Heat Pinch, Mass Pinch, Water Pinch and Hydrogen Pinch (whenever an “amount” has a “quality”)

Process, Energy and System

Summary of Process Integration

T. Gundersen

Sum 24

More on the Grand Composite Curve

160°

Compressor

C2

130°

Condenser

Process, Energy and System

210°

270°

Distillation

Column

50°

H1

160°

210°

C1

Feed

Reboiler

60°

220°

Product

H2

Heat Integration −Introduction

T. Gundersen

Extra 01

270ºC - - - - - - - 250ºC

720 kW

H1

+ 720

230ºC - - - - - - - 210ºC

500 kW

C2

180 kW

- 520

200 kW

220ºC - - - - - - - 200ºC

2000 kW

720 kW

- 1200

880 kW

800 kW

180ºC - - - - - - - 160ºC

360 kW

400 kW

+ 400

C1

440 kW

160ºC - - - - - - - 140ºC

1800 kW

1980 kW

H2

+ 180

70ºC - - - - - - - - 50ºC

220 kW

+ 220

60ºC - - - - - - - - 40ºC

ΔTmin= 20°C

CW

Grand Composite

Curve is based

on the Heat

Cascade

Process, Energy and System

The necessary

data are modified

Temperatures and the

corresponding Heat Flows

Heat Integration −Targeting

T. Gundersen

Extra 02

ST

HP

250

T0’ = 260 QH,min = 1000

+ 720

MP

200

T1’ = 220 R1 = 1720

- 520

150

LP

T2’ = 210 R2 = 1200

- 1200

100

Question: Is this

another Pinch?

T3’ = 170 R3 = 0

+ 400

50

T4’ = 150 R4 = 400

+ 180

Q (kW)

CW

0

T5’ = 60 R5 = 580

+ 220

0

500

1500

T6’ = 50 QC,min = 800

CW

Grand Composite Curve

(or Heat Surplus

Diagram)

Process, Energy and System

Heat Integration −Targeting

T. Gundersen

Extra 03

T0’ = 260 QH,min = 1000

+ 720

T1’ = 220 R1 = 1720

- 520

T2’ = 210 R2 = 1200

- 1200

T3’ = 170 R3 = 0

Answer: No

+ 400

T4’ = 150 R4 = 400

+ 180

0

T5’ = 60 R5 = 580

+ 220

T6’ = 50 QC,min = 800

CW

Grand Composite Curve

T' (°C)

HP

250

MP

200

Process, Energy and System

150

LP

100

50

Q (kW)

CW

0

500

1500

Heat Integration −Targeting

T. Gundersen

Extra 04

300

HP

250

PP

MP

UP

200

150

UP

LP

100

50

Q(kW)

CW

0

0

500

1000

1500

2000

2500

“New” CCs based on Heat Surplus and Deficit Part of Gr.CC and balanced by Hot and Cold Utilities (not representative for Area demand)

Process, Energy and System

Another way of showing it is not another Process Pinch

Heat Integration −Targeting

T. Gundersen

Extra 05

True Balanced Composite Curves with Utilities

(Notice difference in shape and scale)

300

250

PP

200

Process, Energy and System

150

UP

UP

100

50

Q(kW)

0

0

1000

2000

4000

6000

7000

3000

5000

Heat Integration −Targeting

T. Gundersen

Extra 06

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