Water Reuse/Recycle. Can this be Performed Economically in Today s Mills

Transcription

1 Water Reuse/Recycle Can this be Performed Economically in Today s Mills Spring Eastern Canada BLRBAC/ PAPTAC Steam and Steam Power meeting June 22-23, 2010 Presented by Paul Sehl, Regional Sales Manager GE Water and Process Technologies

2 Typical water streams These streams can be broken into two groups High solids (pulp fines), organics, chemical waste Low solids, low organics Economically Attractive

3 Example Pulp and Paper UF system Recovered waters are primarily chemical free and raw water that is being recycled Dry End Recycle Tank 5-27C Fresh Water Save All Tank 52C Warm Tater Tank 5-27C Shower Water Tank 55C Fresh Raw Water direct from the river 5-40 NTU Tempering water goes here 3 x L-128 Zeeweed UF Systems 1900 L/min/train Blending Tank L 30C ~3575 lpm Mechanical Strainer 90% recovery Low Temp UF Filtered Water Tank L 30C See second sheet ~3208 lpm

4 Example Pulp and Paper UF system Low Temp UF Filtered Water Tank L 30C ~3208 lpm Low Temp ~782 lpm Paper Machine Flocculent Dye Map Analyser Refiners Seal Paper machine 55C High Temp ~1188 lpm ~480 lpm chemistry Chemical and silica pushing water ~708 lpm shower Med pressure felt showers Central roll needle shower PU press, 1 st, 3 rd Valrock Paper machine 55C High Temp ~1238 lpm ~683 lpm chemistry Chemical and silica pushing water Squirt tank Valrock shower ~555 lpm shower Med pressure felt showers Central roll needle shower PU press, 1 st, 3 rd 4 th, Valrock

5 Cost Justification Energy Savings Reduced maintenance of the Paper Machine water related systems Improved consistency of chemical addition to the paper making process Better paper quality Improved machine up time The least money saved was on water

6 An Ultrafiltration (UF) system removes Dirt only We may have need for water that also has mineral removal Reverse Osmosis Electrodialysis Reversal (focus for today)

7 EDR A brackish water desalination technology Water recoveries up to 94% Self-cleaning with Polarity Reversal Needs less pretreatment than RO Chlorine-tolerant membranes

8 An EDR Cell Pair

9 EDR Feed Water Normal Feed TDS 200-3,000 mg/l Feed Water Design Limitations Iron (dissolved) 0.3 mg/l Manganese (dissolved) 0.1 mg/l H 2 S 0.1 mg/l Aluminum 0.1 mg/l COD 50 mg/l as O 2 TOC 15 mg/l Oil 2.0 mg/l (IR method) Allowable Levels Continuous Intermittent Free Chlorine 0.5 mg/l 30 mg/l cleaning Turbidity 0.5 NTU 2.0 NTU SDI

10 EDR RO Comparison Criteria EDR RO Feed TDS (mg/l) 400 3, ,000 Salt Removal 50 95% 90 99% System Recovery 85 94% 50 80% Feed Water Turbidity SDI 5 < 12 SDI 15 < 5 Continuous Feed Free Cl mg/l 0 mg/l (TFC) Operating Pressure < 50 psi > 100 psi Power Consumption Lower for < 2,500 ppm TDS Lower for > 2,500 ppm TDS Typical Membrane Life 7 10 years 3 5 years Silica Removal 0% 90 97% Silica in Concentrate Unlimited 250 mg/l

11 What is Electrodialysis? In a salt bath under the influence of direct current, the cations & anions migrate towards their respective electrode. This is the basis for all electrolytic driven processes. Flow of electrons (e - ) Na + Cl - Cl 2 H 2 O 2 OH - H + Cathode (-) (+) Anode

12 Cation Exchange Membrane

13 Anion Exchange Membrane

14 Electrodialysis Cathode (-) Na Na + Na + Cation-Transfer Membrane Na + Cl- Cl Na + Na + Na + Na + Na + Na + Cl- Cl- Na+ Cl- Cl- Na + Cl- Na + Na+ Na + Cl- Cl- Cl- Desalinated Product Anion-Transfer Membrane Concentrate Cation-Transfer Membrane Anode (+) The use of membranes composed of ion exchange material creates separate desalinated and concentrate compartments.

15 Electrodialysis Reversal Process Electrodialysis Reversal is a continuous self-cleaning electrodialysis process by means of periodic reversal of the DC polarity

16 Scale and Colloids: Deposition and Removal

17 Polarity Reversal System reverses 4 times per hour Breaks up freshly precipitated scale and flushes them before they grow and cause damage Reduces slime or similar formations on membrane surfaces Eliminates need for continuous chemical feeds Automatically cleans electrodes with acid formed during anodic operation

18 Streams in the EDR Process

19 Optimal Salt Removal (50 94%) Feed Product STAGE 1 STAGE 2 STAGE 3 STAGE 4 50% 75% 87.5% 94 % 1000uS 500uS 250uS 125uS Example

20 EDR Phased Reversal Diagram

21 Silica ED & EDR do not remove or concentrate silica Silica is not ionized below ph 9.5 High silica levels in the feed No impact on water recovery Example: 5.3 mgd EDR plant in Gran Canaria 85 % water recovery 70 mg/l silica in the feed

22 Example System Layout 8 Trains with each Train in a 3 stage mode Flow rates of usgpm