water pinch (full)

Water Pinch AnalysisWater Pinch AnalysisWater Pinch AnalysisWater Pinch Analysis

Dominic FOO, PhD, PEngDept of Chem & Env Eng

University of Nottingham Malaysia

Copyright@Dominic Foo Pinch Analysis for Water Recovery 2

About myselfAbout myselfAbout myselfAbout myself

� Current position: Associate Professor (University Nottingham Malaysia Campus)

� Qualifications:�BEng (Chemical) (Hons.) (UTM)

�MEng (Chemical) (UTM)

�PhD (Chemical Engineering) (UTM)

� Areas of work:�Research (material recovery, process design &

integration)

�Education (undergraduate/post graduate/ profession training)

�Advice for career & professional development


Talk outlineTalk outlineTalk outlineTalk outline

� Domestic & industrial water usage

� Water pinch analysis

�Graphical targeting for water reuse/recycle

�Nearest neighbour algorithm for network design

�Algebraic targeting for water reuse/recycle & regeneration

� Conclusion


Residential water useResidential water useResidential water useResidential water use


Water usage in our daily lifeWater usage in our daily lifeWater usage in our daily lifeWater usage in our daily life

Flower watering

(3 minutes, 120 Litres)

Teeth brushing


Shower


Hand washing


(Sin Chew Jit Pow, 8 Oct 2003)


Water usage in our daily lifeWater usage in our daily lifeWater usage in our daily lifeWater usage in our daily life

Toilet flushing

(13.5 Litres / flush)

Washing machine

(2 days once, 130 Litres)

Washing plates


Car wash (with host)


(Sin Chew Jit Pow, 8 Oct 2003)


(Smith, 2005)

Water use in process plantWater use in process plantWater use in process plantWater use in process plant


Conventional water networkConventional water networkConventional water networkConventional water network

Process 1

Process 2

Process 3

Process 4

Wastewater

112.5 t/h

Fresh water

112.5 t/h

20.0 t/h

30.0 t/h

37.5 t/h

5.0 t/h


(Wang & Smith, 1994, 1995)

Better water utilisation schemesBetter water utilisation schemesBetter water utilisation schemesBetter water utilisation schemes

Process 1

Process 2

RegenerationProcess 1

Process 2

Regeneration

Regeneration-reuse Regeneration-recycling

Process 1

Process 2

Reuse

Process 1

Recycle


Limiting composite curveLimiting composite curveLimiting composite curveLimiting composite curveLimiting composite curveLimiting composite curveLimiting composite curveLimiting composite curve

2 7 37 41

C (ppm)

∆m (kg/h)

100

400

800

50

456

Process 3

Process 1

Process 2

Process 4


Mass transferMass transferMass transferMass transferMass transferMass transferMass transferMass transfer--------based operationbased operationbased operationbased operationbased operationbased operationbased operationbased operation

Water for vessel washing

Wastewater generated from washing process

Vessel

Washing

Sour gas

Water

Sour water for regeneration

Sweet gasAbsorption


NonNonNonNonNonNonNonNon--------mass transfer processesmass transfer processesmass transfer processesmass transfer processesmass transfer processesmass transfer processesmass transfer processesmass transfer processes

Boiler blowdownBoiler

Cooling tower make-up water

Cooling

tower

Utility make-up & blowdown

O2

NH3

C3H6

AN + H2O

C6H5NO2

Fe

H2O

C6H5NH2 +

Fe3O4

Reactant & by-product formation

Aniline production Acrylonitrile production


An An An An An An An An AcrylonitrileAcrylonitrileAcrylonitrileAcrylonitrileAcrylonitrileAcrylonitrileAcrylonitrileAcrylonitrile ““““““““ANANANANANANANAN”””””””” PlantPlantPlantPlantPlantPlantPlantPlant

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam

Wastewater to Biotreatment

Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales

6.0 kg H2O/s5.0 kg AN/s

5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s

A poor recycleA poor recycleA poor recycleA poor recycleA poor recycleA poor recycleA poor recycleA poor recycle


FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?FW elimination in scrubber ?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?FW elimination in the boiler?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber FW elimination in both scrubber & boiler ?& boiler ?& boiler ?& boiler ?& boiler ?& boiler ?& boiler ?& boiler ?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s

Fresh waterFresh water


Stream segregation?Stream segregation?Stream segregation?Stream segregation?Stream segregation?Stream segregation?Stream segregation?Stream segregation?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s



Add a purification unit?Add a purification unit?Add a purification unit?Add a purification unit?Add a purification unit?Add a purification unit?Add a purification unit?Add a purification unit?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Separator


Defining separation technologiesDefining separation technologiesDefining separation technologiesDefining separation technologiesDefining separation technologiesDefining separation technologiesDefining separation technologiesDefining separation technologies

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Ion Exchange Extraction


Or hybrid separation?Or hybrid separation?Or hybrid separation?Or hybrid separation?Or hybrid separation?Or hybrid separation?Or hybrid separation?Or hybrid separation?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Ion Exchange

Extraction


In different order?In different order?In different order?In different order?In different order?In different order?In different order?In different order?

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Ion Exchange

Extraction


The problem statementsThe problem statementsThe problem statementsThe problem statementsThe problem statementsThe problem statementsThe problem statementsThe problem statements

� Is there any possibility of water reuse in this process?

� How to minimise the fresh water usage?

� How much wastewater flowrates can be reduced?

� Where to place a water purifier?

Is there an optimal solution???


Is there a quickIs there a quickIs there a quickIs there a quick----kill solution?kill solution?kill solution?kill solution?


Recent advances in pinch analysisRecent advances in pinch analysisRecent advances in pinch analysisRecent advances in pinch analysis

1970s Synthesis of heat exchanger network (HEN)

1994 Water minimisation (water pinch)

1989 Synthesis of mass exchange network (MEN)

2002 Property integration (property pinch)

2007 Energy planning (carbon pinch)

1987 Synthesis of HEN for batch processes

Graphical targeting Graphical targeting Graphical targeting Graphical targeting Graphical targeting Graphical targeting Graphical targeting Graphical targeting –––––––– Material Material Material Material Material Material Material Material

Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram Recovery Pinch Diagram

(El-Halwagi et al., 2003; Prakash & Shenoy, 2005)


Water reuse/recycleWater reuse/recycleWater reuse/recycleWater reuse/recycle

Process 1

Process 2

Process 1

Process 2

Regeneration

Process 1

Process 2

Regeneration

Reuse

Regeneration-reuse

Regeneration-recycling

(Wang & Smith, 1994, 1995)

Process 1

Recycle

Current focus


Graphical approach Graphical approach Graphical approach Graphical approach –––– Material Material Material Material recovery pinch diagram (MRPD)recovery pinch diagram (MRPD)recovery pinch diagram (MRPD)recovery pinch diagram (MRPD)


Source: A stream which contains the targeted species. Each source has: �Flowrate Fi�Impurity concentration Ci

�Impurity load:mi = Fi Ci

Source: A stream which contains the targeted species. Each source has: �Flowrate Fi�Impurity concentration Ci

�Impurity load:mi = Fi Ci

Sink/source representationSink/source representationSink/source representationSink/source representationSink/source representationSink/source representationSink/source representationSink/source representation

Sink: An existing process unit/ equipment that can accept a source. Each sink has: �Flowrate Fj�Impurity concentration Cj

where: Cj

min≤ Cj≤ Cjmax

�Load capacity: mi = Fi Ci

Sink: An existing process unit/ equipment that can accept a source. Each sink has: �Flowrate Fj�Impurity concentration Cj

where: Cj

min≤ Cj≤ Cjmax

�Load capacity: mi = Fi Ci

Source iSegregated sources

j = 1

j = 2

Sinks j

?j = 3

i = 1

i = 2

i = 3

(El-Halwagi, 2006)


Water sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN case

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s Water source ???


Water sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN caseWater sinks & sources for AN case

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam-jet Ejector

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


TechnicalTechnicalTechnicalTechnicalTechnicalTechnicalTechnicalTechnical constraints constraints constraints constraints constraints constraints constraints constraints i. Scrubber

� 5.8 ≤ flowrate of wash feed (kg/s) ≤ 6.2

� 0.0 ≤ NH3 content of wash feed (ppm) ≤ 10.0

ii. Boiler feed water � NH3 content = 0.0 ppm

� AN content = 0.0 ppm

iii. Decanter� 10.6 ≤ feed flowrate (kg/s) ≤ 11.1

iv. Distillation column� 5.2 ≤ feed flowrate (kg/s) ≤ 5.7

� 0.0 ≤ NH3 content of feed (ppm) ≤ 30.0

� 80.0 ≤ AN content of feed (wt%) ≤ 100.0

Upper bound

Lower bound

Upper bound

Lower bound


Limiting water data for AN caseLimiting water data for AN caseLimiting water data for AN caseLimiting water data for AN caseLimiting water data for AN caseLimiting water data for AN caseLimiting water data for AN caseLimiting water data for AN case

Water sinks, SKj Flowrate Concentration

j Stream Fj (kg/s) Cj (ppm)

1 Boiler feed water (BFW) 1.2 0

2 Scrubber 5.8 10

Water sources, SRi Flowrate Concentration

i Stream Fi (kg/s) Ci (ppm)

1 Distillation bottoms 0.8 0

2 Off-gas condensate 5.0 14

3 Aqueous layer 5.9 25

4 Ejector condensate 1.4 34


Material recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagramMaterial recovery pinch diagram

� Fulfil the following constraints:� Material flowrate

� Impurity load

� Not limited to water network, other applications include gas & property network.

� Steps required:� Arrange water sinks & sources according to their respective

concentration level in ascending order

� Plot flowrate vs. limiting mass load for all water sinks to form sink composite curve

� Plot flowrate vs. limiting mass load for all water sources to form source composite curve

� Shift source composite to the right & below sink composite


Sink composite curveSink composite curveSink composite curveSink composite curveSink composite curveSink composite curveSink composite curveSink composite curve

Sink, SKj Fj (kg/s) Cj (ppm) mj (mg/s)

SK1 1.2 0 0

SK2 5.8 10 58

ΣΣΣΣj 7.0 58

Lim

itin

g m

ass

lo

ad

(m

g/s

)

Flowrate (kg/s)5 10 15

50

100

150

200

250

300

SK1

SK2


Source composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource Fi (kg/s) Ci (ppm) mi (mg/s)

SR1 0.8 0 0

SR2 5.0 14 70.0

SR3 5.9 25 147.5

SR4 1.4 34 47.6

ΣΣΣΣi 13.1 265.1

Lim

itin

g m

ass

lo

ad

(m

g/s

)


50

100

150

200

250

300

SR1

SR2

SR3

SR4


Source composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource composite curveSource Fi (kg/s) Ci (ppm) mi (mg/s)

SR1 0.8 0 0

SR2 5.0 14 70.0

SR3 5.9 25 147.5

SR4 1.4 34 47.6

ΣΣΣΣi 13.1 265.1

Lim

itin

g m

ass

lo

ad

(m

g/s

)


50

100

150

200

250

300

FFW = 2.1FWW = 8.2


Pure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh sourcePure vs. impure fresh source

Impurity load

Flowrate

Minimum

waste

Maximum

recycle

Pinch

point

Sink

composite

Source

composite

Minimum

fresh

Impurity load

Flowrate

Minimum

waste

Maximum

recycle

Pinch

point

Sink

composite

Source

composite

Minimum

fresh

Impure fresh

locus


Less & over integrationLess & over integrationLess & over integrationLess & over integrationLess & over integrationLess & over integrationLess & over integrationLess & over integration

Impurity load

Flowrate

Minimum

waste

Recycle

Pinch

point

Sink

composite

Source

composite

Minimum

fresh

αααα

αααααααα

Impurity load

Flowrate

WasteRecycle

Infeasible

region

Sink

composite

Source

composite

Fresh

(El-Halwagi, 2006)

Copyright@Dominic Foo Pinch Analysis for Water Recovery 40Copyright@Dominic Foo H84PSD - Process Synthesis & Design Lecture 3 - 40

Significant of the pinch pointSignificant of the pinch pointSignificant of the pinch pointSignificant of the pinch pointSignificant of the pinch pointSignificant of the pinch pointSignificant of the pinch pointSignificant of the pinch point

� The pinch point always located at the pinch causing source

� Some golden rules

�Fresh resource can only be used in lower conc. region

�Sources above the pinch (including fresh feed) should not be fed to sink below the pinch, & may not also mix with sources that are below the pinch concentration.

� The pinch causing source is an exception, as part of it belongs to the region below the pinch.

(Hallale 2002; Manan et al., 2004)

Network design technique Network design technique Network design technique Network design technique ––––

Nearest Nearest Nearest Nearest NeighbourNeighbourNeighbourNeighbour Algorithm (NNA)Algorithm (NNA)Algorithm (NNA)Algorithm (NNA)

(Prakash & Shenoy, 2005a)


Basic principleBasic principleBasic principleBasic principle

� To satisfy a sink, the source to be chosen are the nearest available neighbors to the sink in terms of impurity concentration.

� A source that is just cleaner and a source that is just dirtier than the sink are mixed to satisfy the sink.

SR1

SK150 ppm

SR3SR2

0 ppm 80 ppm 100 ppm

SR1

SK150 ppm

SR3SR2

0 ppm 20 ppm 100 ppm


Basic principleBasic principleBasic principleBasic principle

� If the required amount of a source is not available, then whatever is available of that source is used completely and the next neighbor source is considered to satisfy the sink.

SR1

SK1150 t/h50 ppm

SR3SR2

100 ton/h

0 ppm

1 ton/h

80 ppm

20 ton/h

100 ppm


Important equationsImportant equationsImportant equationsImportant equations

� Assign a pair of neighbours (sources) for the sink:

�Neighbour 1 (N1) – lower C than the sink

�Neighbour 2 (N2) – higher C than the sink

� Solve the flowrate allocation from source i (i.e. i = N1 & N2) to sink j:

�Overall material balance:

� Impurity balance:

jjj FFF SKSK N2,SK N1, =+

jjjj CFCFCF SKSKN2SK N2,1NSK N1, =+


Main steps for NNAMain steps for NNAMain steps for NNAMain steps for NNA1. Arrange sinks/sources in increasing order of C, and start

from sink with lowest Cj.2. Identify source with the same conc. as the sink, i.e. Ci = Cj �

to Step 3; else to Step 4.3. Feed source to the sink when Ci = Cj:

a) If Fi ≥ Fj , source is sufficient to satisfy the sink; to Step 2 for the next sink

b) If Fi ≤ Fj , feed the whole source to the sink, to Step 4

4. Identify the pair of neighbours for the sink; determine the flowrate using Eqs. (1) and (2).

5. Feed source to the sink:a) If Fi,j ≤ the available Fi, the entire sink requirement is met � to Step 2

for next sink.b) If Fi,j ≥ the available Fi, use the entire source & solve for next pair of

neighbours.

6. Repeat Steps 2 – 5 for all sinks.


Example (Example (Example (Example (PolleyPolleyPolleyPolley & & & & PolleyPolleyPolleyPolley, 2000) , 2000) , 2000) , 2000)

20070SK4

10080SK3

50100SK2

2050SK1

15070SR3

100100SR2

25060SR4

5050SR1

Concentration, C (ppm)

Water flowrate, Fi (t/h)

Sources, SRi


Water flowrate, Fj (t/h)

Sinks, SKj

(Answer: FFW = 70 t/h; FWW = 50 t/h; Cpinch = 150 ppm)


Network design with NNANetwork design with NNANetwork design with NNANetwork design with NNA

SK1F = 50 t/hC = 20 ppmm = 1000

SK2F = 100 t/hC = 50 ppmm = 5000

SK3F = 80 t/hC = 100 ppmm = 8000

SR1

SR2

SR3

SR4

20 t/h 65 t/h 35 t/h

25 t/h

30 t/h 35 t/h

SK4F = 70 t/hC = 200 ppmm = 14000

35 t/h

F = 50 t/h

C = 50 ppm

F = 100 t/h

C = 100 ppm

F = 70 t/h

C = 150 ppm

F = 60 t/h

C = 250 ppm

10 t/h

5 t/h

FW

25 t/h

35 t/h30 t/h

F = 70 t/h

C = 0 ppm


Sink/source matching matrixSink/source matching matrixSink/source matching matrixSink/source matching matrix

SR425060

SR315070

SR2100100

SR15050

FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)


Back to AN case againBack to AN case againBack to AN case againBack to AN case againBack to AN case againBack to AN case againBack to AN case againBack to AN case again




2 Scrubber 5.8 10








Network design with NNANetwork design with NNANetwork design with NNANetwork design with NNA

SK1F = 1.2 kg/sC = 0m = 0

SK2F = 5.8 kg/sC = 10m = 58

SR1

SR2

SR3

SR4

F = 0.8 kg/s

C = 0 ppm

F = 5.0 kg/s

C = 14 ppm

F = 5.9 kg/s

C = 25 ppm

F = 1.4 kg/s

C = 34 ppm

FWF = 2.1 kg/s

C = 0 ppm1.7 kg/s0.4 kg/s

4.1 kg/s

8.2 kg/s


Alternative designAlternative designAlternative designAlternative design

SK1F = 1.2 kg/sC = 0m = 0

SK2F = 5.8 kg/sC = 10m = 58

SR1

SR2

SR3

SR4

F = 0.8 kg/s

C = 0 ppm

F = 5.0 kg/s

C = 14 ppm

F = 5.9 kg/s

C = 25 ppm

F = 1.4 kg/s

C = 34 ppm

FWF = 2.1 kg/s

C = 0 ppm0.9 kg/s1.2 kg/s

4.1 kg/s

8.2 kg/s


Network design for reuse/recycleNetwork design for reuse/recycleNetwork design for reuse/recycleNetwork design for reuse/recycle

Reactor

Decanter

Distillation

Column

O2

Aqueous

layer

ScrubberNH3

C3H6

Steam


Off-Gas

Condensate

Condensate

Bottoms

Water

AN to sales


5.1 kg H2O/s

+ Gases Tail gases

to disposal

Boiler

BFW

1.2 kg H2O/s

14 ppm NH3

0.4 kg AN/s

4.6 kg H2O/s

18 ppm NH3

4.6 kg AN/s

6.5 kg H2O/s

10 ppm NH3

4.2 kg AN/s

1.0 kg H2O/s

25 ppm NH3

0.4 kg AN/s

5.5 kg H2O/s

0 ppm NH3

0.1 kg AN/s

0.7 kg H2O/s

1 ppm NH3

3.9 kg AN/s

0.3 kg H2O/s

34 ppm NH3

0.2 kg AN/s

1.2 kg H2O/s

20 ppm NH3

1.1 kg AN/s

12.0 kg H2O/s


Network evolution techniquesNetwork evolution techniquesNetwork evolution techniquesNetwork evolution techniques

(Prakash & Shenoy, 2005b; Ng & Foo, 2006)


Source Shift Algorithm (SSA)Source Shift Algorithm (SSA)Source Shift Algorithm (SSA)Source Shift Algorithm (SSA)

� Objective: To simplify a preliminary networkdesigned by NNA

� 2 main criteria to consider sink-source candidates:

�CSK = CSR

�FSK ≤ FSR

� Main steps:

� Identify the sink-source pairs that fulfil both criteria

�Feed the sink fully with the source

�An equal flowrate of source(s) will be shifted to the sink that was originally fed by the source


SK1F = 100 t/hC = 100 ppm

SK2F = 100 t/hC = 100 ppm

FWF = 50 t/hC = 0 ppm

SR1F = 100 t/hC = 100 ppm

SR2F = 50 t/h

C = 200 ppm

25 25

25 25

50 50(50)

(25)

(25)

(a) (b)

SK2F = 100 t/hC = 100 ppm

SK1F = 100 t/hC = 100 ppm


SR1F = 100 t/hC = 100 ppm

SR2F = 50 t/h

C = 200 ppm

100

50

50

A simple exampleA simple exampleA simple exampleA simple example


Another configurationAnother configurationAnother configurationAnother configuration

SK1F = 100 t/hC = 100 ppm

SK2F = 100 t/hC = 100 ppm


SR1F = 100 t/hC = 100 ppm

SR2F = 50 t/h

C = 200 ppm

25 25

25 25

50 50(50)

(25)

(25)

(a) (b)

SK2F = 100 t/hC = 100 ppm

SK1F = 100 t/hC = 100 ppm


SR1F = 100 t/hC = 100 ppm

SR2F = 50 t/h

C = 200 ppm

100

50

50



20070SK4

10080SK3

50100SK2

2050SK1

15070SR3

100100SR2

25060SR4

5050SR1



Sources, SRi



Sinks, SKj



Identifying sinkIdentifying sinkIdentifying sinkIdentifying sink----source pairssource pairssource pairssource pairs

2535SR425060

253510SR315070

6535SR2100100

3020SR15050

53530FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)


Interconnections: 12 Interconnections: 12 Interconnections: 12 Interconnections: 12 �� 11 11 11 11 �� 10101010

2535SR425060

253510SR315070

6535SR2100100

3020SR15050

53530FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)

5

15

10

80

40

10

20

25

2560

5010


Water Path Analysis (WPA)Water Path Analysis (WPA)Water Path Analysis (WPA)Water Path Analysis (WPA)

� Definition: a continuous route which starts from a fresh source, linked with the sink-source connections, and end at a waste sink.

� Objective: Generate alternative networks by adding fresh resource penalties.

� Analogy:� Utility path in removing the smallest heat exchanger unit in HEN

(Linnhoff et al., 1982; Smith, 1995, 2005).

� Mass-load path to reduce number of mass exchangers in MEN (El-Halwagi, 1997).

� Heuristic: to minimise water penalty, remove the smallest match among all L-kink connections within all available water paths.


Identifying water pathsIdentifying water pathsIdentifying water pathsIdentifying water paths

5010SR425060

6010SR315070

8020SR2100100

3020SR15050

4030FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)


Remove 2 matches with 10 t/h FWRemove 2 matches with 10 t/h FWRemove 2 matches with 10 t/h FWRemove 2 matches with 10 t/h FW

5010SR425060

6010SR315070

8020SR2100100

3020SR15050

4030FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)

50

60

7010

10


Remove 3 matches with 30 t/h FWRemove 3 matches with 30 t/h FWRemove 3 matches with 30 t/h FWRemove 3 matches with 30 t/h FW

60SR425060

70SR315070

8020SR2100100

3020SR15050

5030FW070

WWSK4SK3SK2SK1SK

j

SRi

Ci(ppm)F

i(t/h)

2001005020Cj(ppm)

50708010050Fj(t/h)

20

50

5020

20

Algebraic approach Algebraic approach Algebraic approach Algebraic approach Algebraic approach Algebraic approach Algebraic approach Algebraic approach ––––––––

Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis Water Cascade Analysis

(Manan et al., 2004; Foo et al., 2006)


Graphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approachesGraphical vs. algebraic approaches

Graphical approachGraphical approach

� Advantages� Good insights of the

problems

� Intuitive

� Limitations� Tedious solution for

complex problem

� Inaccuracy problems

� Scaling problems/ dimensionality

Algebraic ApproachAlgebraic Approach

� Advantages

� Computational effectiveness

� Ease for large & complex problems

� Interaction with other softwares, e.g. process simulators, spreadsheets

� Limitations� Less insight on the problem


Concept of material cascadingConcept of material cascadingConcept of material cascadingConcept of material cascadingConcept of material cascadingConcept of material cascadingConcept of material cascadingConcept of material cascading

100 ppm

100 kg/s

200 ppm

–50 kg/s

100 kg/s

(waste)

100 kg/s

(fresh source)

100 ppm

100 kg/s

200 ppm

–50 kg/s

100 kg/s

50 kg/s(waste)

Without reuse Reuse


General formGeneral formGeneral formGeneral formGeneral formGeneral formGeneral formGeneral form

k Ck ΣΣΣΣj Fj ΣΣΣΣi Fi ΣΣΣΣi Fi −−−− ΣΣΣΣj Fj F

C, k ∆∆∆∆m kCum. ∆∆∆∆mk

FF

k Ck (Σ

jFj)1

(ΣiFi)1

(ΣiFi− Σ

jFj)1

FC, k ∆m

k

k + 1 Ck+1 (Σ

jFj)k+1

(ΣiFi)k+1

(ΣiFi− Σ

jFj)k+1

Cum. ∆mk+1

FFW, k+1

FC, k+1 ∆m

k+1

……

…

……

…

……

…

……

…

……

…

……

…

……

…

……

…

……

…

n – 2 Cn–2 (Σ

jFj)n-2

(ΣiFi)n-2

(ΣiFi− Σ

jFj)n-2

FC, n–2 ∆m

n–2

n – 1 Cn–1 (Σ

jFj)n-1

(ΣiFi)n-1

(ΣiFi− Σ

jFj)n-1

Cum. ∆mn–1

FFW, n–1

FC, n–1

= FW ∆m

n–1

n Cn Cum. ∆m

nFFW, n

FW

FW,

Cum.

CC

mF

k

kk

−

∆=


Example of WCA Example of WCA Example of WCA Example of WCA Example of WCA Example of WCA Example of WCA Example of WCA –––––––– AN productionAN productionAN productionAN productionAN productionAN productionAN productionAN production




2 Scrubber 5.8 10








Infeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascade

kCk

(ppm)ΣΣΣΣj Fj

(kg/s)ΣΣΣΣi Fi

(kg/s)ΣΣΣΣi Fi - ΣΣΣΣj Fj

(kg/s)FC

(kg/s)∆∆∆∆m

(mg/s)Cum. ∆∆∆∆m

(mg/s)(kg/s)

1 0 1.2 0.8 -0.4

-0.4 -4

2 10 5.8 -5.8 -4 -0.40

-6.2 -24.8

3 14 5 5 -28.8 -2.06

-1.2 -13.2

4 25 5.9 5.9 -42 -1.68

4.7 42.3

5 34 1.4 1.4 0.3 0.01

6.1 6099792.6

6 1000000 6099792.9 6.10

FW

FW,

Cum.

CC

mF

k

kk

−

∆=


Feasible cascade Feasible cascade Feasible cascade Feasible cascade Feasible cascade Feasible cascade Feasible cascade Feasible cascade

kCk

(ppm)ΣΣΣΣj Fj

(kg/s)ΣΣΣΣi Fi


(kg/s)FC

(kg/s)∆∆∆∆m


(mg/s)

FFW = 2.06

1 0 1.2 0.8 -0.4

1.66 16.57

2 10 5.8 -5.8 16.57

-4.14 -16.57

3 14 5 5 0.00

0.86 9.43 (PINCH)

4 25 5.9 5.9 9.43

6.76 60.81

5 34 1.4 1.4 70.24

FWW = 8.16 8156865.51

6 1000000 8156935.76


Water allocation targetsWater allocation targetsWater allocation targetsWater allocation targetsWater allocation targetsWater allocation targetsWater allocation targetsWater allocation targets

kCk

(ppm)ΣΣΣΣj Fj

(kg/s)ΣΣΣΣi Fi


(kg/s)FC

(kg/s)∆∆∆∆m


(mg/s)

FFW = 2.06

1 0 1.2 0.8 -0.4

1.66 16.57

2 10 5.8 -5.8 16.57

-4.14 -16.57

3 14 5 5 0.00

0.86 9.43 (PINCH)

4 25 5.9 5.9 9.43

6.76 60.81

5 34 1.4 1.4 70.24

FWW = 8.16 8156865.51

6 1000000 8156935.76

Pinch causing source

(Manan et al., 2004)

Lower conc.

region

Higher conc.

region



20070SK4

10080SK3

50100SK2

2050SK1

15070SR3

100100SR2

25060SR4

5050SR1



Sources, SRi



Sinks, SKj



Infeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascadeInfeasible cascade

4

5

k Ck ΣΣΣΣj Fj ΣΣΣΣi Fi ΣΣΣΣi Fi - ΣΣΣΣj Fj FC ∆∆∆∆m Cum. ∆∆∆∆m

01 20

2

3

6

7 106

F

F,

Cum.

CC

mF

k

kk

−

∆=


Feasible cascadeFeasible cascadeFeasible cascadeFeasible cascadeFeasible cascadeFeasible cascadeFeasible cascadeFeasible cascade

4

5

k Ck ΣΣΣΣj Fj ΣΣΣΣi Fi ΣΣΣΣi Fi - ΣΣΣΣj Fj FC ∆∆∆∆m Cum. ∆∆∆∆m

FFW = _______1 20

2

3

6FWW = _______

7 106

Targeting for water regenerationTargeting for water regenerationTargeting for water regenerationTargeting for water regeneration

(Ng et al., 2007, 2008)


Water regenerationWater regenerationWater regenerationWater regenerationWater regenerationWater regenerationWater regenerationWater regeneration

Process 1

Process 2

Process 1

Process 2

Regeneration

Process 1

Process 2

Regeneration

Reuse

Regeneration-reuse

Regeneration-recycling

(Wang & Smith, 1994, 1995)

Process 1

RecycleCurrent focus


Process 1

Process 3 Process 4

Process 2

FW WW

Reuse

Recycle

FW : fresh water WW : wastewater

Reuse

Water reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle schemeWater reuse/recycle scheme


Regeneration processes(concentration/pressure driven)

Mass separating agents Power/pressure

FW : fresh water WW : wastewater RW : regenerated water

Water reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regenerationWater reuse/recycle + regeneration

Process 1

Process 3 Process 4

Process 2

FW

WW

RW


Example (Example (Example (Example (Example (Example (Example (Example (PolleyPolleyPolleyPolleyPolleyPolleyPolleyPolley & & & & & & & & PolleyPolleyPolleyPolleyPolleyPolleyPolleyPolley, 2000) , 2000) , 2000) , 2000) , 2000) , 2000) , 2000) , 2000)

Sinks, SKj



SK1 50 20

SK2 100 50

SK3 80 100

SK4 70 200

Sources,

SRi



SR1 50 50

SR2 100 100

SR3 70 150

SR4 60 250



AlgorithmAlgorithmAlgorithmAlgorithmAlgorithmAlgorithmAlgorithmAlgorithm

Assumptions:

1. Fixed regen outlet concentration (Cout)

2. Cost of regeneration is omitted

Source(s) is shifted to the FWR from highest

Cj until ΣjFj= ΣiFi in the RWR

Set regeneration concentration, Cout

Preliminary allocation – water sinks/sources are separated

into FWR (Ci ,Cj < Cout) and RWR (Ci ,Cj > Cout)

RWR

ΣjFj> ΣiFi

NO

YES

Sink(s) is shifted to the FWR from lowest Cj until

ΣjFj= ΣiFi in the RWR

Additional sink (Fj, A) and source flowrate (Fi, A) are

shifted to the FWR, calculated based on:

Fj Cj = Fi, A (Ci, A – Cj, A)

Ultimate flowrate targets

START

All SKj in the FWR with

Cj= 0 ppm?

YES

NO

END

Determine FFW and FWW in FWR

Total FRW = FRW, FWR + FRW, RWR

FRW, FWR is added at Cout in FWR

Calculate FRW, FWR = ((Fj× Cj)/ CF)

ΣiFi (with Ci higher than

Cout) ≤ FRW, FWR

Note: FWR – fresh water regionRWR – regenerated water region


Preliminary allocation (Preliminary allocation (Preliminary allocation (Preliminary allocation (Preliminary allocation (Preliminary allocation (Preliminary allocation (Preliminary allocation (CCCCCCCCoutoutoutoutoutoutoutout = 10 ppm)= 10 ppm)= 10 ppm)= 10 ppm)= 10 ppm)= 10 ppm)= 10 ppm)= 10 ppm)

k C ΣjFj

Σi Fi

Σi Fi− Σ

i Fj

FC ∆m

kCum ∆m

k

FFW = 70.00

1 0 0 70 1.41.4

2 20 50 -50 20 0.62

3 50 100 50 -50 -30 -1.50.5

4 100 80 100 20 -10 -0.50

5 150 70 70 60 3 (PINCH)3

6 200 70 -70 -10 -0.52.5

7 250 60 60 FWW= 50.00 49987.549990

11 106 0

Total 300 280

Cout = 10 ppm

No FW is used here

May use both FW or RW








RWR

ΣjFj> ΣiFi

NO

YES


ΣΣΣΣjFj= ΣΣΣΣiFi in the RWR

Additional sink (Fj, A) and source flowrate (Fi, A)

are shifted to the FWR, calculated based on:



START


Cj= 0 ppm?

YES

NO

END






Cout) ≤ FRW, FWR


Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of sink(ssink(ssink(ssink(ssink(ssink(ssink(ssink(s) & ) & ) & ) & ) & ) & ) & ) & source(ssource(ssource(ssource(ssource(ssource(ssource(ssource(s))))))))FWR RWR

C ΣjFj Σi Fi C ΣjFj Σi Fi0 Cout= 10

20 20 20 30

50 50 100 50

100 100 80 100

150 150 70

200 200 70

250 250 60

106 106

Total 20 Total 280 280

Why should we use FW this source can tolerate dirty water? Can we maximise its load?








RWR

ΣjFj> ΣiFi

NO

YES


ΣΣΣΣjFj= ΣΣΣΣiFi in the RWR

Additional sink (Fj, A) and source flowrate (Fi, A)

are shifted to the FWR, calculated based on:



START


Cj= 0 ppm?

YES

NO

END






Cout) ≤ FRW, FWR

Sink of the lowest Cj

Sources of the lowest Ci & positive value in the ΣiFi –ΣjFj column of WCT


Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of Reallocation of sink(ssink(ssink(ssink(ssink(ssink(ssink(ssink(s) & ) & ) & ) & ) & ) & ) & ) & source(ssource(ssource(ssource(ssource(ssource(ssource(ssource(s))))))))FWR RWR

C ΣjFj Σi Fi C ΣjFj Σi Fi0 Cout= 10

20 20 + 5 20 30 – 5

50 50 100 50

100 + 5 100 80 100 – 5

150 150 70

200 200 70

250 250 60

106 106

Total 20 + 5 5 Total 275 275








RWR

ΣjFj> ΣiFi

NO

YES


ΣjFj= ΣiFi in the RWR

Additional sink (Fj, A) and source flowrate (Fi, A) are

shifted to the FWR, calculated based on:



START


Cj= 0 ppm?

YES

NO

END






Cout) ≤ FRW, FWR


FW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWR

kCk

(ppm)ΣΣΣΣj Fj(t/h)

ΣΣΣΣi Fi(t/h)

ΣΣΣΣi Fi - ΣΣΣΣj Fj(t/h)

FC

(t/h)∆∆∆∆m

(kg/h)Cum. ∆∆∆∆m

(kg/h)(t/h)

FFW =____

1 0

2 20 25 -25

3 50

4 100 5 5

FWW=____

5 106

Total 25 5

FW

FW,

Cum.

CC

mF

k

kk

−

∆=


FW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWRFW & WW targeting in FWR

kCk


ΣΣΣΣi Fi(t/h)


FC

(t/h)∆∆∆∆m


(kg/h)

FFW =______

1 0

0.40

2 20 25 -25 0.40

-0.15

3 50 0.25

-0.25

4 100 5 5 0.00

0.00

5 106 FWW =_____ 0.00

Total 25 5


RW

FW,

Cum.

CC

mF

k

kk

−

∆=k

Ck(ppm)

ΣΣΣΣj Fj(t/h)

ΣΣΣΣi Fi(t/h)


FC

(t/h)∆∆∆∆m


(kg/h) (t/h)

1 Cout= 10 FRW = ____

2 20 25 -25

3 50 100 50 -50

4 100 80 95 15

5 150 70 70

6 200 70 -70

7 250 60 60

FRW = ____8 106

Total 275 275

RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)RW targeting in RWR (infeasible)


RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)RW targeting in RWR (feasible)

kCk


ΣΣΣΣi Fi(t/h)


FC

(t/h)∆∆∆∆m


(kg/h)FRW = ________

1 Cout= 10

53.57 0.54

2 20 25 -25 0.54

28.57 0.86

3 50 100 50 -50 1.39

-21.43 -1.07

4 100 80 95 15 0.32

-6.43 -0.32

5 150 70 70 0.00

63.57 3.18

6 200 70 -70 3.18

-6.43 -0.32

7 250 60 60 2.86

FRW = ________ 0.54

8 106 53560

Total 275 275


Nearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithmNearest neighbour algorithm

� Apply NNA (Prakash & Shenoy, 2005) based on the 2 general equations:

�Overall material balance:

� Impurity balance:

� Design separately for FWR & RWR.

jjj FFF SKSK N2,SK N1, =+

jjjj CFCFCF SKSKN2SK N2,1NSK N1, =+


Network design with NNANetwork design with NNANetwork design with NNANetwork design with NNANetwork design with NNANetwork design with NNANetwork design with NNANetwork design with NNA

SK1F = 50 t/hC = 20m = 1000

SK2F = 100 t/hC = 50m = 5000

SK3F = 80 t/hC = 100m = 8000

SR1

SR2

SR3

SR4

SK4F = 70 C = 200m = 14000

F = 50

C = 50

F = 100

C = 100

F = 70

C = 150

F = 60

C = 250

RW

FFW = 20 t/h

FRW = 53.57 t/h

FWW = 0 t/h

F = 53.57

C = 10

FWF = 20

C = 0 20

5

From FWR

From FWR

18.75

6.25

6.43

63.57

3.57

70

6.43

25

43.75

31.25

Reg

eneration

53.57


Comparison of various casesComparison of various casesComparison of various casesComparison of various cases

020Regeneration

5070Reuse/recycle

280300Base case

FWW (ton/h)FFW (ton/h)Polley & Polley

7.31.2Regeneration*

8.22.1Reuse/recycle

13.17.0Base case

FWW (kg/s)FFW (kg/s)AN case

* Your own exercise


Concluding remarksConcluding remarksConcluding remarksConcluding remarks

� Process integration techniques provide a bird’s eye view on the maximum extend of water recovery.

� Always proceed from options with lower capital investment/complexity.

� Targeting ahead of design!


ReferencesReferencesReferencesReferencesReferencesReferencesReferencesReferences� El-Halwagi, M. M., Gabriel, F. and Harell, D. (2003). Rigorous Graphical Targeting for Resource Conservation

via Material Recycle/Reuse Networks. Industrial & Engineering Chemistry Research. 42: 4319-4328.

� Foo, D. C. Y., Manan, Z. A. and Tan, Y. L. (2006b). Use Cascade Analysis to Optimize Water Networks, Chemical Engineering Progress. 102(7): 45-52 (July 2006).

� Manan, Z. A., Tan, Y. L. and Foo, D. C. Y. (2004). Targeting the Minimum Water Flowrate Using Water Cascade Analysis Technique AIChE Journal. 50(12): 3169-3183.

� Ng, D. K. S. and Foo, D. C. Y. (2006). Evolution of Water Network with Improved Source Shift Algorithm and Water Path Analysis, Industrial and Engineering Chemistry Research. 45, 8095-8104.

� Ng, D. K. S., Foo, D. C. Y. Tan, R. R. and Tan, Y. L. (2007). Ultimate Flowrate Targeting with Regeneration Placement, Chemical Engineering Research and Design, 85 (A9) 1253–1267.

� Ng, D. K. S., Foo, D. C. Y. and Tan, R. R. (2008). Extension of Targeting Procedure for ‘Ulltmate Flowrate Targeting with Regeneration Placement’ by Ng et al., Che. Eng. Res. Des. 85 (A9): 1253 – 1267. Chemical Engineering Research and Design, 86(10), 1182-1186.

� Polley, G. T. and Polley, H. L. (2000). Design Better Water Networks. Chem Eng Progress. 96(2): 47-52.

� Prakash, R. and Shenoy, U. V. (2005a). Targeting and Design of Water Networks for Fixed Flowrate and Fixed Contaminant Load Operations. Chemical Engineering Science. 60(1): 255-268.

� Prakash, R. and Shenoy, U. V. (2005b). Design and Evolution of Water Networks by Source Shifts. Chemical Engineering Science. 60(7), 2089-2093.

� Rosain, R. M. (1993). Reusing Water in CPI Plants. Chemical Engineering Progress, 89(4): 28-35.

� Smith, R. (2005). Chemical Process Design and Integration. John Wiley & Sons, New York.

� Wang, Y. P. and Smith, R. (1994). Wastewater Minimisation. Chemical Engineering Science. 49: 981-1006.

� Wang, Y. P. and Smith, R. (1995). Wastewater Minimization with Flowrate Constraints. Chemical Engineering Research and Design, Part A. 73: 889-904.


Dominic C. Y. Foo,Dominic C. Y. Foo,Dominic C. Y. Foo,Dominic C. Y. Foo, PhD, PhD, PhD, PhD, PEngPEngPEngPEng�[email protected]

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