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Water Conservation In Pulp & Paper IndustryThrough Innovative Water Management &
Modeling Techniques.
R. M. Mathur, B.P. Thapliyal, A.K. Goel
Central Pulp And Paper Research InstituteP.O.Box. 174, Saharanpur
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Pulp and paper industry is one of the major water
consuming industries.Water is used for a variety of processes and gets
contaminated during processing with raw
materials,chemicals, by-products & residues.Treatment of contaminated wastewater has
always been an expensive & technically
challenging subject.
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Water Consumption In Indian Paper Mills
Raw Material Products Water Consumptionm3/tBamboo Writing/Printing Paper
100-120
Wood+Bamboo Writing/Printing Paper 90-125
Wood+Bamboo Writing/Printing Paper
Unbleached varieties
80-120
Wood+Bamboo+RCF News print 95
Agro Residues Writing/Printing Paper 100
RCF News print/ writingPrinting
35
Market Pulp Speciality Paper 90
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Bleaching
30%
Paper
Machine
25%
Pulping
14%
Chemical
Recovery
10%
Power House
6%
Stock
Preparation
4%
Others
11%
Typical Water Consumption in Wood/ BambooBased Mill
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Water management techniques can prove to
be highly effective as they enable efficient
usage of water with considerations of
reuse, recycle and
regeneration opportunities.
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Process Integration
The application of methodologies aimed at
designing/modernizing an Industrial Facility by
optimizing its various constituent units rather
than improving each individual unit by itself.
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Process Integration Methods
Classical pinch based
Mathematical programming based
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Graphical technique to minimize fresh waterflow
An extension of the pinch analysis
technique for heat integration.Water surplus diagrams are utilized to
target water requirement.
Pinch Based Approach
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Water Pinch Composite Curves
Each water related
process operation
considered as having
water inputs and
output streams and
composite of water
demand (Input) and
water sources (Output)
can be constructed.
Concen
tra
tio
n
Water Flow
Waste water
Fresh Water
Water Pinch
Water Demands
Water Sources
Purity
Not suitable for multiple contaminant systems
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The pinch point ( pinch concentration and pinch
mass load) is calculated by application ofComposite Table Algorithm (CTA).
A system of equations is solved with constraints to
get values for various water streams.
A Network is generated by applying NearestNeighbor Algorithm (NNA)
Network of all possible matches is created and
the system is optimized for minimum fresh water
requirement based on capital/operating
expenses.
Mathematical Programming Approach
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Provides a robust way of water network design.
Provides insight into water targeting with a
consideration of recycle, reuse & regeneration.
Advantages of
Mathematical Programming Approach
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Basic Network Structure
A basic integrated water network consists of a set of
water using and water treating operations.
Each water using operation demands a certain quality
and quantity of water to satisfy its process needs.
This demand may be fulfilled by mixing fresh water with
effluent streams from other water using operations and
regenerated water.
The process outlet streams may be used to satisfy the
demand of other operations, sent to treatment units or
discharged without treatment.
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Process
C P in C P out
C Water out C Water in
C P in
C P out
C Wout
C W in
m, Mass flow rate
Conce
tra
tio
n
Unit operation mass flow
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Mill Details:-
Production 75,000 tpaProducts - Printing and writing papers
Raw materials - hardwood and bamboo , ratio(84:16)6 paper machines
3 stationary batch digesters
Pulp is bleached by using C/DEopD1D2 bleaching
sequence.
CASE STUDY
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The study was carried out for two contaminants(TS & COD) in the bleach plant for reuse &
recycle options.
A complete water balance of the pulp mills wasprepared using online & portable flow meters.
The water samples from various streams were
characterized with respect to their pollution load.
METHODOLOGY
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Water Balance Flow Diagram for Mill
( All Figures in m3/hr)
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Data Extraction:
All operations assumed to be fixed contaminant
(FC) and fixed flowrate operations type. Thelimiting contaminant levels are fixed at 10 %
above the current values.
Restriction on re use of water streamsAll matches prohibited by pH are
disallowed.
Order and flowrate from one processto another is maintained
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Fig. Extracted Flow Diagram
368 368
1854 2970
403 403
1190 2081
367 367
1037 1910
373 373
990 1447
847847
656 656
CD
Pulp washing
EOPPulp washing
D1
Pulp washing
D2
Pulp washing
DeckerPulp washing
D 1
D 2
D 3
D 4
D 5
S 1
S 2
S 3
S 4
S 5
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Composite Table Algorithm..m...C - Cmin
Flow
Concentration,
ppm
Net Flow,
t/hr
Load
Kg/hr
CumulativeLoad, kg/hr
(m) Slope
d 847 600 0 0 0 0
s 847 656 847 47.4 47.4 72.3
d 373 990 0 0.0 47.4 47.9
d 367 1037 373 17.5 65.0 62.6
d 403 1190 740 113.2 178.2 149.7
s 373 1447 1143 293.8 471.9 326.1
d 368 1854 770 313.4 785.3 423.6
s 367 1910 1138 63.7 849.1 444.5
s 403 2081 771 131.8 980.9 471.4
s 368 2970 368 327.2 1308.0 440.4
3000 0 0.0 1308.0 436.0
Pinch pointPinch LoadPinch conc.
Flow = FlowDemand - Flow Source
Flow x ( C2 C1)/1000
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Limiting Composite Curve
3000
2500
2000
1500
1000
500
250 500 750 1000 1250 15000
Contaminant Load, kg/hr
C
on
tam
ina
ntC o
ncen
tra
tion,
ppm
Limiting Composite Curve
Water Composite curve
Pinch LinePinch Concentration
Pinch Load
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Nearest Neighbour Algorithm
Sources which are immediate higher/ lower
in concentration for a demand are mixed in
ratio determined by mass balance to
satisfy the demand.
If the required flow rate is not available fora source, than whatever is available of that
source is used completely & next neighbor
is considered to satisfy the demand.
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Nearest Neighbour Algorithm
The mass balance equations are-
FSK , DP + FS(K+1), DP = FDPFSK , Dp CSK +FS(K+1),DP CS(K+1) =FDP CDPWhere
F&C are flowrate & concentration
SK & S(K+1) are immediate cleaner& dirtier
sources ( Nearest Neighbour)
DP is the particular demand.
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Proposed Water Balance Network for Mill -1
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Results for Mill I
Particulars Min. Fw UnitsMin. Fresh WaterConsumption before PI
191 m3/hrMin. Fresh Water after PI(considering TS and
COD as contaminants)
121 M3/hr
Fresh Water Saving % 36 -
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& ,
HANK YOU
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