water minimization through pinch technology

8/2/2019 Water Minimization Through Pinch Technology

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Water Minimizationthrough Pinch

technology

Ankara, September 13-15 2010

Jose R. AlvarezDepartment of Chemical and Environmental Engineering

UNIVERSITY OF OVIEDO


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Water Pinch Technology

Systematic technique for analyzing water networks andreducing water costs for processes. Aims to identify andselect the best water re-use, regeneration and effluenttreatment opportunities.

Avoid End-Of-Pipe solutions

May be applied to almost any industrial water systemwhere there are users of fresh water and producers ofwaste water. It can also analyze small systems.

More restrictions = less scope for water savings. Good solutions:

save water reduce capital investment recover valuable raw materials


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Applicability

The savings achieveddepend greatly on theproject objectives.

Capital cost savingsoften play a major role inthe deliverables of a waterpinch study.

Identifying and deployingthe best water re-usesystems is a challenge.

Industry Water

Reduction

Chemical &Fibers 25 %

Corn processing 25 %

Oil refining 30 %

Chemicals 40 %

Paper mill 20 %

Coal chemicals 50 %

Polymers (batch) 60 %

Military Base 40 %


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Water Uses in IndustryWaste Water Streams

RAW WATER

TREATMENT

RAW

WATER

FRESH

WATER

BFW

TREATMENT

WASTEWATER

TREATMENT

STEAM

SYSTEM

PROCESS 1

PROCESS 2

PROCESS 3

WASTE

WATER

CONTAMINATED

STORM WATER

Condensate

loss

Boiler blowdown

Cooling tower blowdown

Ion exchange regeneration

Discharge

Steam


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Principles for Saving Water

Re-use (no concentration changes)

Re-use (with changes to inletconcentration)

Regeneration and re-use

Distributed effluent treatment


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Re-Use (no concentration changes)

Begin with the assumption that the existingconcentrations are the maximum limits.

This normally identifies a few small re-useopportunities.

To achieve further savings we must challenge theassumptions made for concentration limits.


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Re-Use (with changes to inletconcentration)

Identify projects where large water savings are possible byincreasing the upper concentration limits to selected sinks.

This will normally identify a few large re-use opportunities.


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Distributed Effluent Treatment(de-centralized effluent treatment systems)

Streams are segregated into categories and treated appropriatelybefore mixing with other streams.

Several small scale treatment units are used that operate onundiluted effluent streams rather than one large unit operating on

very dilute effluent. The resulting system can offer better removal efficiency at reduced

cost.


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Variants of Water Pinch

Method 1: UMIST

based on contaminant generation

and concentration limitationswhich give limiting profiles and targets

Method 2: LM (Linnhoff March)

based on known available sourcesand known demands

which give targets and water use


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C

m

CPROC, INCPROC, OUT

CW, OUT

CW, IN

C

m

CPROC, INCPROC, OUT

Water

Profiles

CPROC, IN CPROC, OUT

CW, OUT CW, IN

Process Stream

Water Stream

Mass Transfer

f

fW

C

m

Process(CW, OUT)max

(CW, IN) max

Limiting Water Profile

C

m

Process Limiting Water Profile

Water Supply Lines


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Concentration vs mass

transported diagram

T

DH

TPROC, INTPROC, OUT

TW, OUT

TW, IN

C

m

CPROC, IN

CPROC, OUT CW, OUT

CW, IN

DT = 1/CP DH DC = 1/Q Dm


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UMIST approach

Maximum use of water

Maximum water inlet concentration

Maximum water outlet concentration

Restrictions:

Minimum driving force for mass transfer

Solubility limits

Scaling and deposit formation Corrosion limits

Minimum flow to avoid sedimentation ofsuspended solids


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Example. One contaminant

after R. Smith, UMIST

PROCESS 2

PROCESS 3

PROCESS 4

PROCESS 1C

m

Process

(CW, OUT)max

(CW, IN) max



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Example : One contaminant

after R. Smith, UMIST

PROCESS 2

PROCESS 3

PROCESS 4

PROCESS 1C

m

CW, OUT

CW, IN


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Example: One contaminant

From Wang and Smith, ,-Wastewater Minimization,Chemical Engineering Science, 1994, 49(7):981-1006

ProcessingUnit

CIN, max(ppm)

COUT,max(ppm)

ContaminantGeneration (kg/h)

Limiting WaterFlowrate (t/h)

Process 1 0 100 2 20

Process 2 50 100 5 100

Process 3 50 800 30 40

Process 4 400 800 4 10

Sum: 41 kg/h From C:s

and Gener.


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Data AnalysisProcessingUnit

CIN, max(ppm)

COUT,max(ppm)



Process 1 0 100 2 20

Process 2 50 100 5 100

Process 3 50 800 30 40

Process 4 400 800 4 10

FRESH

WATER

112.5 t/h

PROCESS 1

PROCESS 2

PROCESS 3

WASTE

WATER

112.5 t/h

PROCESS 4

20 t/h

50 t/h

37.5 t/h

5 t/h

PROCESS 1

0

100

200

300

400

500

0 2 4 6 8 10

m (kg/h)

C

(ppm)

PROCESS 2

0

100

200

300

400

500

0 2 4 6 8 10

m (kg/h)

C

(ppm)

PROCESS 3

0

200

400

600

800

1000

0 10 20 30

m (kg/h)

C

(ppm)

PROCESS 4

0

200

400

600

800

1000

0 1 2 3 4 5

m (kg/h)

C

(ppm)

Process 1 Process 2

Process 3 Process 4

170 t/h


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Pinch AnalysisComposite Curves

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

ppm)

PINCH

2 5 20 4


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Concentration

interval, ppm

Process 1,

kg/h

Process 2,

kg/h

Process 3,

kg/h

Process 4,

kg/h

Total ,

kg/h

Accumulated,

kg/h

0 - 50 1 1 1

50 - 100 1 5 2 8 9

100 - 400 12 12 21

400 - 800 16 4 20 41

Total 2 5 30 4 41


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0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

ppm)

PINCH

2 5 20 4 1 8 12 20


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0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

1 8 12 20

C

m

(CW, OUT)max

(CW, IN) max



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0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

ppm)

PINCH

2 5 20 4 1 8 12 20

90 t/h


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Water distribution


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Water distribution

90 ton/h0 ppm

P120 ton/h0 ppm

70 ton/h

0 ppm

20 ton/h100 ppm

50 ton/h

0 ppm

20 ton/h0 ppm

P2

2 kg/h

5 kg/h50 ton/h

100 ppm

P320 ton/h

800 ppm

16 kg/h

20 ton/h800 ppm

14 kg/h

45.7 ton/h

800 ppm

5.7 ton/h100 ppm

44.3 ton/h

100 ppm

P4 5.7 ton/h800 ppm

4 kg/h


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Water distribution

Concentration

interval, ppm

Process 1,

kg/h

Process 2,

kg/h

Process 3,

kg/h

Process 4,

kg/h

Total ,

kg/h

Accumulated,

kg/h

0 - 50 1 (1) 1 1

50 - 100 1 (1) 5 (5) 2 (2) 8 9

100 - 400 12 (6) (6) 12 21

400 - 800 16 (8) (8) 4 (4) 20 41

Total 2 (2) 5 (5) 30(16)(14) 4 (4) 41


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ProcessingUnit

CIN, max(ppm)

COUT,max(ppm)



Process 1 0 100 2 20

Process 2 50 100 5 100

Process 3 50 800 30 40

Process 4 400 800 4 10

Sum: 41 kg/h From C:s

and Gener.


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Water distribution


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One Possible Solution

44.3 t/h

20 t/h

20 t/h 70 t/h

Water

90 t/h

Process 3

Process 4

Process 2

Process 1


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Possible designs

Choose e.g. from economical considerations


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Further possibilities: Minimumregeneration and minimum fresh

water use

F h ibili i Mi i


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Further possibilities: Minimumregeneration and minimum fresh

water use

0

100

200

300

400

500

600

700

800

0 10 20 30 40

m (kg/h)

C

(ppm)


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Regeneration flowrate. At the pinch

Minimum regeneration

Minimum fresh water use


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Minimum Regeneration


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Water distribution

46.2ton/h0 ppm

P120 ton/h0 ppm

26.2 ton/h

0 ppm

20 ton/h100 ppm

P2

2 kg/h

2.62 kg/h26.2 ton/h

100 ppm

P3

16.7 kg/h

45.8 ton/h

800 ppm

P4 5.7 ton/h800 ppm

4 kg/h

46.2ton/h100 ppm

46.2ton/h5 ppm

REGENERATION

P225.1 ton/h5 ppm

21.1 ton/h

5 ppm

25.1 ton/h100 ppm

21.1 ton/h800 ppmP3

19 ton/h100 ppm

6.1 ton/h100 ppm

19 ton/h

800 ppm

5.7 ton/h100 ppm

0.4 ton/h

100 ppm

2.38 kg/h

13.3 kg/h


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Water distribution

Concentration Process 1, Process 2, Process 3, Process 4, Total , Accumulated,

interval, ppm kg/h kg/h kg/h kg/h kg/h kg/h

0 - 50 1 (1) 1 1

50 - 100 1 (1) 5 (2.62) 2 (2) 8 9

(2.38)

100 - 400 12 (6.3) 12 21

(5.7)

400 - 800 16 (8.4) 4 (4) 20 41

(7.6)

Total 2 (2) 5 (2.62) 30 (16.7) 4 (4) 41

(2.38) (13.8)


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Minimum Regeneration


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Minimum Fresh water


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Minimum Fresh water


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Water distribution

P120 ton/h0 ppm

20 ton/h100 ppm

2 kg/h

P3

16.7 kg/h

P4 5.7 ton/h800 ppm

4 kg/h

46.2ton/h100 ppm

73.7 ton/h5 ppmREGENERATION

P2

52.6 ton/h

5 ppm

21.1 ton/h5 ppm

21.1 ton/h

800 ppm

P3

18.9 ton/h

100 ppm

33.7 ton/h100 ppm

18.9 ton/h

800 ppm

5.7 ton/h100 ppm

28 ton/h100 ppm

5 kg/h

13.3 kg/h

52.6 ton/h

100 ppm

REGENERATION

REGENERATION

REGENERATION


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Water use. Cost optimization

FRESH REGENERATED IMPLICATIONS

90 Ton/h0 Ton/h Minimum fresh water

46.2 Ton/h 46.2 Ton/h Reduce fresh waterReduce wastewater

20 Ton/h 73.7 Ton/h Increase watertreatment


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Linnhoff March approachBy Linnhoff March (now KBC)

List of available sources

flow rates and contaminant levels

List of demanded flows (sinks) flow rates and contaminant levels

cumulative chart gives pinch and

fresh water needed waste water produced

process flows and improvements


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Sources, Sinks and UnitOperations

Process. Water flow rates arefixed.

Utility. Water flow rates canbe changed (i.e., city water).May have minimum andmaximum flow limits together

with two cost terms: fixedcost and variable cost.

Sink: The point at which water is consumed.

Source: The point at which a supply of water isavailable.Unit Operation: A piece of equipment or processingunit that acts as both a sink and source for water(takes water in and sends water out).


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SINKS

ProcessingUnit

CIN, max(ppm)

COUT,max(ppm)



Process 1 0 100 2 20

Process 2 50 100 5 100

Process 3 50 800 30 40

Process 4 400 800 4 10

SOURCES


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Project Targets

Waste Minimization: Meeting new environmental regulations. Minimizing the cost of fresh material / waste disposal.

Site Expansion. Likely to need additional fresh water and wastewater capacity.

Avoiding new waste treatment or disposal facilities. Overcoming fresh water availability problems. Avoiding high fees for fresh water / waste disposal.

Debottlenecking. Water systems can be a bottleneck for theoverall production process: Cooling tower throughput. Batch vessel washing. Pump capacity.

P1

P2

S1

S2

P3RA

A

RB

B

P1

P2

S1

S2

P3RA

A

RB

B

P1

P2

S1

S2

P3RA

A

RB

B

P1

P2

S1

S2

P3RA

A

RB

B

P1

P2

S1

S2

P3RA

A

RB

B

P1

P2

S1

S2

P3RA

A

RB

BP1

P2

S1

S2

P3

RAA

RB

B

RC

C

P1

P2

S1

S2

P3

RAA

RB

B

RC

C


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Basic Data Required

Water flows. Key contaminant concentrations. Start with existing

concentration values. For sinks, if you can identify themaximum allowable concentrations, consider these.

Utility costs. For each utility to be considered: cost offresh water, cost of discharge, operating cost ofexisting treatments.

Environmental Limits.

Additional data: Geographical data. Physical location of sources and sinks within the system,

together with capital and operating cost terms based on distance and flow (to getsimpler network designs).

Cost data. Fixed cost and variable cost terms for utility items and connections Treatment and Regeneration specifications: performance characteristics for

the equipment together with cost information.

Bounds for selected variables.


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Selecting Key Contaminants

A key contaminant is "Any property that prevents the directre-use of a waste water stream.

color, temperature, suspended solids, and others.

often the plant operators have valuable contributions.

How many?

Anywhere between 3 and 15 contaminants simultaneouslyin a study.

Good results by considering only 2-5 contaminants forparticular sub-sections of a study.

Select 1, 2 or 3 contaminants to make the analysis easy(particularly if you are new to this technology). If you havetoo many contaminants defined you may make the analysisdifficult and your data collection will take longer and costmore.


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Key questions to ask whenselecting contaminants

Will re-use of water containing this contaminant cause aproblem with the process?

If it does not cause a problem, you do not need to consider it.

Can high levels of the contaminant go to waste?

If not, you will need to consider it when looking at the finaleffluent.

Is the contaminant a problem downstream?

Watch out for product quality issues downstream.

Is the contaminant a problem in just one part of the system?

If this is the case, you could exclude it from the selectedcontaminants, and use bounds to prevent reuse of thecontaminated water to that part of the system.


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Recommended Procedures

Group contaminants into types: Measurements that describegroups of contaminants:

COD (chemical oxygen demand), TOC (total organiccontent)

Suspended solids, Dissolved salts, conductivity.

Organics, Alcohols

and others!

Check existing sources of data: Ideally, the concentrationlevels should not be difficult or expensive to obtain:

Existing material balances

Routine measurements

Previous studies

Laboratory archives


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Math-Derived Limitations

Contaminants do not react with each other whenstreams are blended. This limits the scope forrepresenting chemical reactions that increase orreduce contaminant load.

Contaminants blend linearly. Whenever two or morestreams are mixed, each contaminant is assumed toobey the standard rules of mass balance (conservationof mass, etc.), without interacting with othercontaminants.

Contaminants have linear units of measure. Non-linear measurements such as pH cannot be easilyrepresented.


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Identify Sources and Sinks

If you could change either the source or sink connection fora water stream and still make the same quality product,then the source and sink should be included in the analysis.

Select streams that are relevant for the project objectives Steams that contribute significantly to the contaminant load Streams with significant flow rates.

Steam and Condensate. There are two types of steam users toconsider: Steam users that return clean condensate to be re-used are often

excluded Steam users that do not return condensate for re-use are included

Streams to exclude: Aqueous "Process streams" that cannot be changed (example:

product from reactor A to reactor B) Atmospheric losses from cooling towers, vents, etc. Feed, product, or intermediate streams that contain water.


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Identify Utilities and Costs

Utility: source, sink or unit operation whose water flowrates can be changed during the water pinch analysis.

Typical utilities for a water pinch study include:

Utility Sources Utility Sinks Utility UnitOperations

Town / city water Final effluentdischarge

Filters

Demineralized water Road / rail / shipdisposal

Reverse osmosis

Well water Biological treatment

For each utility you should know realistic costs on aconsistent basis. For new treatment equipment, the costmight also be chosen to reflect the technological risk ofuntried or unproven technologies.


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Common Unit Operations

Reverse Osmosis

Backwash Filter

Precipitator Dissolved Air Flotation

Air Stripper

Steam Stripper Ion Exchange

Generic Treater


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Source/demand chart


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Design and Water Allocation

Graphical methods not always useful

especially if several contaminants

Problem solved with mathematicaloptimization algorithms (MILP-MINLP)

give ultimate optimum?

Commercial programs exist(WaterTargetTM)


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Optimization approachesMixed-integer Linear/Nonlinear Programming

},}1,0{|{

},,|{

,

0),(..

),(min

aAyyyY

bBxxxxRxxX

YyXx

yxgts

yxfZ

m

ULn

Objective function

Constraints

f(x,y) andg(x,y) linear =>

Branch and Bound Beale (1958), Balas (1962), Dakin (1965)

MILP Cutting planes Gomory (1959), Balas et al (1993)Branch and cut Johnson, Nemhauser & Savelsbergh (2000)

f(x,y) andg(x,y) nonlinear =>

Branch and Bound method

Ravindran and Gupta (1985) Tawarmalani,Sahinidis (2002)

MINLP Generalized Benders Decomposition Geoffrion (1972)Outer-Approximation

Duran & Grossmann (1986), Fletcher & Leyffer (1994)


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Summary

Water management demanded by:

environmental limits

water availability and price

reduced effluents (amount, concentrations)

energy consumption and price

Some reductions in fresh water consumptioncan be achieved by heuristics and pinchtechnology analysis

Bigger reductions / total closure demandsinternal cleaning

Water allocation and energy demand interactwith each other: analyze simultaneously?.


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Jose R. Alvarez

Water Managementthrough Pinch

technology

Department of Chemical and Environmental Engineering

UNIVERSITY OF OVIEDO

water minimization through pinch technology

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