Central Pulp And Paper Research Institute P.O.Box. 174, Saharanpur

1. Water Conservation In Pulp & Paper Industry Through Innovative Water Management & Modeling Techniques. R. M. Mathur, B.P. Thapliyal, A.K. Goel Central Pulp And Paper Research Institute P.O.Box. 174, Saharanpur

2. 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.

3. Water Consumption In Indian Paper Mills

4. Typical Water Consumption in Wood/ Bamboo Based Mill

5. Water management techniques can prove to be highly effective as they enable efficient usage of water with considerations of • reuse, • recycle and • regeneration opportunities.

6. 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.

7. Process Integration Methods • Classical pinch based • Mathematical programming based

8. Pinch Based Approach • Graphical technique to minimize fresh water flow • An extension of the pinch analysis technique for heat integration. • Water surplus diagrams are utilized to target water requirement.

9. Purity Fresh Water Water Sources Concentration Water Demands Water Pinch Waste water Water Flow 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. • Not suitable for multiple contaminant systems

10. Mathematical Programming Approach • The pinch point ( pinch concentration and pinch mass load) is calculated by application of Composite Table Algorithm (CTA). • A system of equations is solved with constraints to get values for various water streams. • A Network is generated by applying Nearest Neighbor Algorithm (NNA) • Network of all possible matches is created and the system is optimized for minimum fresh water requirement based on capital/operating expenses.

11. Advantages of Mathematical Programming Approach • Provides a robust way of water network design. • Provides insight into water targeting with a consideration of recycle, reuse & regeneration.

12. 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.

13. C P in C P out Process C Water out C Water in C P in C W out Concetration C P out C W in m, Mass flow rate Unit operation mass flow

14. Process 4 800 Concetration Process 3 400 Water Supply Line 100 Process 1& 2 m, Mass flow rate m, Mass flow rate Water limiting profile Limiting Profile curve

15. CASE STUDY • Mill Details:- • Production 75,000tpa • Products - 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.

16. METHODOLOGY • 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 was prepared using online & portable flow meters. • The water samples from various streams were characterized with respect to their pollution load.

17. Water Balance Flow Diagram for Mill ( All Figures in m3/hr)

18. Data Extraction: • All operations assumed to be fixed contaminant (FC) and fixed flowrate operations type. The limiting contaminant levels are fixed at 10 % above the current values. • Restriction on re use of water streams • All matches prohibited by pH are disallowed. • Order and flowrate from one process to another is maintained

19. 368 368 S 1 CD D 1 1854 2970 Pulp washing 403 403 EOP S 2 D 2 Pulp washing 1190 2081 367 367 D1 S 3 D 3 Pulp washing 1037 1910 373 373 D2 S 4 D 4 Pulp washing 990 1447 847 847 Decker S 5 D 5 Pulp washing 656 656 Fig. Extracted Flow Diagram

20. Flow rate and Contamination Data for Mill

21.  Flow =  FlowDemand - FlowSource  Flow x ( C2 – C1)/1000 ………..m……... C - Cmin Pinch conc. Pinch Load Pinch point Composite Table Algorithm

22. 3000 2500 2000 1500 1000 500 0 250 500 750 1000 1250 1500 Limiting Composite Curve Water Composite curve Pinch Line Pinch Concentration Contaminant Concentration, ppm Limiting Composite Curve Pinch Load Contaminant Load, kg/hr

23. 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 for a source, than whatever is available of that source is used completely & next neighbor is considered to satisfy the demand.

24. Nearest Neighbour Algorithm The mass balance equations are- FSK, DP + FS(K+1),DP = FDP FSK, Dp CSK +FS(K+1),DP CS(K+1) =FDP CDP Where F&C are flowrate & concentration SK & S(K+1) are immediate cleaner& dirtier sources ( Nearest Neighbour) DP is the particular demand.

25. Fresh water Network before study

26. Fresh Water Network After Study

27. Proposed Water Balance Network for Mill -1

28. Results for Mill –I

29. Conclusion • The study conducted in selected mills in the pulp mill section has shown that PI studies can be a valuable tool for water conservation. • Application of the mathematical programming model developed for water minimization has shown scope of water savings in both the mills after selecting suitable water networks.

30. THANK YOU