DM water production through Reverse Osmosis(RO)

I tried to explain how DM water can be produced through ultra filtration (UF) and Reverse Osmosis(RO), What parameters should be maintained etc

1. Production of Demineralized (DM) Water Through Ultra-Filtration(UF) & Reverse Osmosis (RO) Presented by Raghab Gorain Emp No. 104892 Final - Term Appraisal A Maharatna Company Date- 08/09/2017 NTPC Darlipali 1

2. Coal Storage Conveyer Belt Coal Pulverizer Furnace Boiler Turbine Condenser Generator Transformer Fly Ash Chimney ESP DM Plant PT Plant Cooling Tower Bus Bar Overview OF Thermal Power Plant Eco Bottom Ash Raw Water 2

3. DM Plant FeCl 3 PE Lime NaOCL Acid NaOH UF CIP Tank Anti scalant Anti oxidant (SMBS) Acid ( HCl ) DM Tank-1 (2400m 3 ) DM Tank-2 (2400m 3 ) RO Tank (170 m 3 ) UF Tank ( 317m 3 ) RO RO MCF Skid-1 Skid-2 RO Reject Sludge 267.8m 3 / hr 7.8m 3 / hr 260m 3 / hr Backwash Filter UF 180m 3 / hr Sand Filter Sump Basket Strainer HP Pump 71m 3 / hr (2W+1S) 61m 3 / hr (2W+1S) 120m 3 / hr (2W+1S) Degasser Tower Clarifier Aerator Reservoir MB RO Per. Tfr. Pump A B C Cl 2 3

4. Pretreatment of water Impurities present in Raw water Suspended impurities Ionic solids Micro-organisms Dissolved G asses Treatment of water in PT plant Mainly four steps are used to remove the impurities in raw water Oxygenation- Aeration of the water to precipitate out the ferric salt. Here ferrous salts are converted to ferric salt and also it removes the dissolved CO 2 Coagulation- In this process a flux mixture is produced by the addition of FeCl 3 and polyelectrolyte . Flocculation & Settlement- It is the process to precipitate out the solids from the clarifier. Filtration - To remove the impurities Aeration of water Water Reservoir 4

5. Pretreatment of Water Exposing the raw water to atmospheric air. So some of the dissolved salts oxidized, specially ferrous and manganous bicarbonate as follows 4Fe(HCO 3 ) 2 + O 2 + 2H 2 O =4Fe(OH) 3 + 8CO 2 2Mn(HCO 3 ) 2 + O 2 = 2MnO 2 + 4CO 2 + 2H 2 O Aeration Clarification FeCl 3, PAC :used as flocculating agent Lime : To maintain pH Cl 2 : As disinfectant Schulze-Hardy rule Greater the valency of the flocculating ion, greater will be its coagulation power. Fe 3+ ion is 1000 times more effective than that of monovalent ion. So FeCl 3 is used in clarifier. Fe 3+ + PO 4 3- = FePO 4 Cl 2 +H 2 O = HOCl + HCl Gravity Sand Filter(GSF) It is used to remove the suspended particles and the microbial organisms from the clarified water. Filtered water turbidity: <5 NTU Residual Cl 2 : 0.2-0.5 ppm GSF 5

6. Ultra-Filtration(UF) System UF(Filtered water supply Pumps) Required Flow 180 m 3 / hr Pump 3(2W+1S) (Each 90 m 3 / hr ) Basket Strainer No. of stream 2(Both Working) Flow per stream(m 3 / hr ) 90 Material of Construction SS316 Size 100 m UF Membrane Make Hyflux Material of construction Polyether sulphone Water flow type Out to in Permeate Flow per stream(m 3 / hr ) 80 % of Recovery 95 No of skid 2 Total membrane per skid 25 UF Backwash Pump No of pumps 2(1w+1s) Required Flow per membrane(m 3 / hr ) 6 Total no of membrane per Skid 25 Required backwash flow(m 3 / hr ) 150 6

7. Parameters Value pH 6.5 -7.5 Temperature( o C ) 20-35 TSS(ppm) <4 Turbidity(NTU) <4 COD BDL BOD BDL Fe & Mn <0.3 and Nill Oil and Grease Nill UF Inlet parameters UF Module UF CIP Tank UF Tank Basket Strainer Air Compressor UF Backwash Pump Backwash Waste CIP waste UF Feed Sump UF Outlet parameters Parameters Value SDI <3 Turbidity <0.2 NTU Ultra-Filtration(UF) System 150m 3 / hr (1W+1S) 7

8. Cleaning of UF membrane NaOH NaOCl HCl No of Tank 2W 2W 2W Capacity(m 3 ) 0.5 0.5 0.5 Cleaning pump flow(m 3 / hr ) 100 100 100 Dosage(ppm ) 150 400 300 Required quantity as available(kg/ hr ) 104.17 500 166.67 Sp. Gravity @25 o C 1.45 1.15 1.18 Concentration of fluid(w/w) 48% 10% 30% Solution feed flow(LPH) 71.84 434.78 141.24 Dosing time(Min.) 10 10 10 No of pumps used 2(1w+1s) 2(1w+1s) 2(1w+1s) Provided Pump capacity(LPH) 100 500 200 Chemical Dosing in UF 8

9. Cleaning of UF membrane Maintenance cleaning is a semi automated sequence meant short-term regaining of permeability.MC involves a short duration (60 min.) cleaning with chlorine and HCl . MC should be conducted one in every 72 hrs. Maintenance Cleaning(MC) Cleaning Chemicals and their concentrations NaOH & NaOCl NaOCl 400 ppm (Free chlorine should be 200 ppm) NaOH 11 pH(150ppm) MC1 MC2 HCl HCl 2.5 pH (300ppm) Recovery Cleaning (RC) High pH NaOCl 400 ppm + NaOH 11 pH (150 ppm) Low pH 2.5 pH (300ppm) Cleaning Frequency UF Running hrs 71 72 144 216 288 360 432 504 576 Cleaning Service MC1 MC1 MC1 MC2 MC1 MC1 RC MC1 After 6 MC 1 recovery cleaning will be done 9

10. UF System UF Permeate water storage Tank No. of Tank 1 Available Capacity(m 3 ) 317 Effective volume per meter height(m 3 ) 52.83 UF Air Blower Pump No. of Blowers 2(1w+1s) Available Capacity(Nm 3 / hr ) 71 Type of Blower Twine Lobe UF CIP Tank Provided capacity(m 3 ) 3 UF CIP Pump No. of pump 2(1w+1s) Provided flow per each pump(m 3 / hr ) 100 UF Permeate transfer pump No. of pump 3(2w+1s) Flow through each pump(m 3 / hr ) 71 10

11. Reverse Osmosis(RO) Micron Cartridge Filter(MCF) RO Inlet MCF RO CIP MCF Make Parker Hannifin (USA) No. 3(2w+1s) 1(w) Material of filter media Polypropylene Polypropylene Design flow rate(m 3 / hr ) 71 64 Max. allowable press. Drop(KSC) 0.5 0.5 Efficiency 90% Size(Nominal) 5 m 5 m 11

12. RO High Pressure Pump No. 3(2w+1s) Flow through each Pump (m 3 / hr ) 71 Chemical Dosing in RO Acid Antiscalant Antioxidant No of Tank 2 2 2 Capacity(m 3 ) 1.7 0.2 0.1 RO Feed flow(m 3 / hr ) 142 142 142 Dosage(ppm ) 25 5 5 Required quantity as available(kg/ hr ) 71 14.2 7.1 Sp. Gravity @25 o C 1.07 1.05 1.1 Concentration of fluid(w/w) 5% 5% 10% Solution feed flow(LPH) 67 14 7 Dosing time(Min.) 10 10 10 No of pumps used 2(1w+1s) 2(1(w+1s) 2(1w+1s) Provided Pump capacity(LPH) 100 20 10 Cleaning of RO membrane 12

13. RO Dosing Chemicals A nd T heir Functions Hydrochloric Acid ( HCl ): It maintains the pH of the RO inlet water. It decreases the pH Antioxidant: Sodium meta bisulphite (SMBS) is used as anti oxidant. In the RO feed water if any oxidizing agent (like Cl, ozone etc ) will be present then it will damage the RO membranes. Under alkaline pH conditions, chlorine attack is faster than at neutral or acidic pH and it will catalyze the membrane degradation. So antioxidant SMBS is used to remove the free Cl and as a biostatic. When Na 2 S 2 O 5 is dissolved in water then it will form sodium bisulphite (SBS) Na 2 S 2 O 5 + H 2 O = 2NaHSO 3 Free chlorine forms HOCl in water. Cl 2 + H 2 O = HOCl + HCl HOCl oxidize the RO membrane, so we have to remove this one and NaHSO 3 reduces the HOCl . 2NaHSO 3 + 2HOCl → H 2 SO 4 + 2HCl + Na 2 SO 4 Antiscalant : In the RO feed water carbonate, phosphate and sulphate salt of Ca, Mg etc. are present that will form scale in the RO membrane. So we have to remove these. Anti scaling agent is used to remove these salts. 13

14. RO System RO Permeate water storage Tank No. of Tank 1 Available Capacity(m 3 ) 137 out of 170 Effective volume per meter height(m 3 ) 28.33 RO Air Blower Pump No. of Blowers 2(1w+1s) Available Capacity(Nm 3 / hr ) 2460 Type of Blower Centrifugal Blower RO CIP Tank Provided capacity(m 3 ) 3.6 RO CIP Pump No. of pump 2(1w+1s) Provided flow per each pump(m 3 / hr ) 115 RO Permeate transfer pump No. of pump 3(2w+1s) Flow through each pump(m 3 / hr ) 61 Degasser Tower No. of DG Tower 2(1w+1s) Design Flow(m 3 / hr ) 123 14

15. Particle Rejection and Passage by MF, UF, RO Micro - Filter Size of Removable particle( m m ) 0.1-0.4 Removed particle Bacteria,Flocculted material, TSS Passage materials Macromolecules, dissolved solids Ultra-Filtration(UF) Size of Removable particle( m m) 0.1-0.01 Removed particle Colloid particles, protein, microbiological molecules, Large organic molecules Passage materials Surfactants, dissolve solids, smaller molecules, acids & alkaline compounds Trans-membrane Pressure(bar) 1-7 Reverse Osmosis(RO) Size of Removable particle( m m) 0.0001-0.001 Removed particle Removed 99% dissolved materials,(95-97)% dissolved organics, 98% colloidal and biological matters Passage materials Few ions smaller than water molecule, like Na + , Ca 2+ , Ag + etc can pass. Salt passage increases in RO system by Effective pressure decrease Temperature increase Feed salt concentration increase Permeate flow decrease 15

16. RO membrane RO Membrane Make Torrey Material of construction Polyamide, Spiral wound Water flow type Out to in RO Feed Flow per stream 70.8 m 3 / hr % of Recovery 87 RO Permeate Flow per stream 61.6 Array of per RO train 8:4:2 Total membrane per skid 25 16

17. Reverse Osmosis Reverse osmosis is separation method where ions, molecules are removed by applying pressure against the osmotic pressure. Here water is passed from low concentrated to high concentrated solution through a semi permeable membrane against the osmotic pressure. RO Membrane RO Permeate RO Reject Salt Rejection: Salt Rejection % = Conductivity of (Feed-Permeate)*100 Conductivity of feed Recovery: Recovery% = Permeate flow rate *100 Feed flow rate RO Membrane RO Permeate RO Reject Concentration Factor Recovery% = 1 (1-% Recovery) Feed Feed Reject RO Membrane Reject Reject RO Membrane Single Stage Double Stage 17

18. Mixed Bed(MB) Mixed Bed No. of Unit 3(2w+1s) Available Capacity(m 3 / hr ) per unit 60 Size of the strainer 1500mm*2300mm ( Dia *Height) Alkali Measuring Tank No. of Tank 3(2w+1s) Provided volume 0.17 m 3 (165 Lt.) Req. vol. per regeneration 162 Lt. Acid Measuring Tank No. of Tank 1 Provided volume 0.15 m 3 (150 Lt.) Req. vol. per regeneration 145 Lt. MB Air Blower Pump No. of Blowers 2(1w+1s) Available Capacity(Nm 3 / hr ) 210 Type of Blower Twine Lobe DM water storage Tank No. of Tank 2 Available Capacity(m 3 ) 2400 Effective volume per meter height(m 3 ) 200 DM Water Make UP Pump No. of Blowers 2(1w+1s) Available Capacity(Nm 3 / hr ) 100 18

19. MB Resin Cation Exchange Resin Anion Exchange Resin Manufacturer Auchtel Auchtel Required quantity(m 3/ MB ) 0.873 1.051 Material of Construction Styrene- divinyle benzene copolymer Styrene- divinyle benzene copolymer Functional Group Sulphonate (-SO 3 - ) -[N(CH 3 )] 3 + Total Exchange Capasity 2 Eq./L 1.3 Eq./L Packing Density(g/L) 800-840 700 Particle Size(mm) 0.3-1.2 0.3-1.2 Chemical stability Insoluble in dilute acids and bases Insoluble in dilute acids and bases Max. Temperature( o C ) 120 60 Min. bed depth(mm) 500 500 Service flow rate(BV/L) 5-40 5-40 Slow Rinse(BV/L) 2 2 Fast Rinse(BV/L) Same as service flow rate Same as service flow rate 19

20. Cation Exchange Resin Cation Exchange Resin Chemicals HCL H 2 SO 4 NaCl Level(g/L) 30-150 40-240 50-250 Flow Rate(BV/ hr ) 2-5 2-10 2-8 Concentration(%) 5-8 0.7-6 8-12 Min. contact time 30 min 2R-H + Na 2 CO 3  2R-Na+H 2 CO 3 Reaction mechanism of Cation exchange Resin During service condition During Regeneration condition R-Na + HCl  R-H + NaCl R= 2

21. Anion Exchange Resin Reaction mechanism of Anion exchange Resin 2R’- OH + H 2 SO 4 R’ 2 SO 4 +2H 2 O During service condition During Regeneration condition R’ 2 SO 4 + NaOH2R’-OH + Na 2 SO 4 Anion Exchange Resin Chemicals NaOH Level(g/L) 30-150 Flow Rate(BV/ hr ) 3-5 Concentration(%) 5-8 Min. contact time 30 min R’= 21

22. DM water production Data Plot(Weekly) DM Water Production Data 6/17/2017 1 6/17/2017 1 6/24/2017 4.9 6/24/2017 4.9 6/30/2017 5.4 6/30/2017 5.4 7/6/2017 5.40 0.00 7/6/2017 5.40 7/13/2017 8.709 7/13/2017 8.709 7/20/2017 10.285 7/20/2017 10.285 7/27/2017 10.549 7/27/2017 10.549 8/2/2017 11.3 1.6 8/2/2017 11.3 8/10/2017 11.3 3.7 8/10/2017 11.3 8/17/2017 6.7 6.1 8/17/2017 6.7 8/23/2017 1.654 7.484 8/23/2017 1.654 22

23. Images of Darlipali Project DM Tank Chemical Building GSF Chimney CPU Boiler ESP Generator DM Control room screen RO skid Water Reservoir 23

24. Acknowledgement Sh. S Ghosh Sir(GM, O&M) Sh. A V S Rao(GM, Operation & Commissioning) Sh. S K Mohanty Sir (AGM, O&M- Chemistry) Seniors of My Department NTPC Darlipali NTPC 24

25. A H Y U N T O K 25