ZERO DISCHARGE PROCESSES USING NEW LOW COST EVAPORATION TECHNOLOGY

Transcription

1

2 ZERO DISCHARGE PROCESSES USING NEW LOW COST EVAPORATION TECHNOLOGY

3 Applicability of different water treatment technologies 3 = high separation 2 = moderate 1 = low separation Note! ph may change rating considerably Dissolved substances Pollutant to remove Cations (e.g. heavy metals) Monovalent ions Multivalent ions Complexed ions Anions Monovalent (e.g. chloride) Multivalent (e.g. SO4 2- ) Technology Adsorption (e.g. activated carbon) Ion exchange Chemical precipitation Membrane technologies Ultrafiltration (UF) Nanofiltration (NF) Reverse osmosis (RO) Electrodialysis Evaporation Distillation Flotation Air/steam stripping Electrical methods Electrolyse Electro coagulation Biological treatment Ammonium Organic compounds Carbohydrates Proteins Alcohols Solvents (e.g. hydrocarbons) Pigments Pesticides COD in general Methods have often to be combined for zero discharge operation or to meet discharge limits

4 EVAPORATION: NATURE S PURIFICATION METHOD

5 PRINCIPLE OF SINGLE EFFECT THERMAL EVAPORATION Condensing T= 100 C p= 1013 mbar(a) Clean water Dissolved solids (pollutants) stay in the water and finally turn into dry matter Effluent Heat transfer surface

6 ZERO DISCHARGE SYSTEM BY EVAPORATION MAKE UP WATER PROCESS CLEAN WATER PRETREATMENT (RO...) WASTE WATER EVAPO- RATION CONCEN- TRATE REUSE OR DISPOSAL 6

7 SINGLE EFFECT EVAPORATION Specific Steam Consumption = 1,1 Vapour Cooling Water CONDENSER Condensate 1,0 Steam 1,1 Feed Concentrate Primary Condensate 7

8 4-EFFECT EVAPORATION Specific Steam Consumption = 0,28 CONDENSER Vapour Cooling Water Feed Vapour Vapour Vapour Steam Vapour Waste Heat Concentrate Primary Condensate Condensate 8

9 MVR EVAPORATION COMPRESSOR P = C x MF x DT P = Fan Power Use (kw) C = Constant (2,5 3) MF = Vapor mass flow (ton/h) DT = Temp. difference ( C) Compressed Vapour DT Vapour Steam consumption ~ 0 Cooling water cons. ~ 0 Feed Concentrate Condensate 9

10 PRIMARY TECHNICAL BENEFITS WITH EVAPORATION IN EFFLUENT TREATMENT Excellent water quality, which can be used for almost any purpose High recovery rate leaving only a small volume of concentrate or solids for reuse or final disposal (eg. solar drying) Substances may be recovered by crystallization Constant capacity and water quality Not sensitive to changes in feed water quality Only simple pre-treatment needed, if any, low or no chemical usage Strict discharge limits can be met 10

11 COST SAVINGS IN WATER RECYCLING BY EVAPORATION Fresh water cost savings, including possible cleaning costs Reduced cost for conventional effluent treatment No cost for sludge handling Cost savings in land allocated for conventional treatment Value of recovered solids (positive or negative) Heating of the water to the process temperature With new technology: The savings can be bigger than the operation costs! 11

12 CONVENTIONAL EVAPORATION PROCESSES Drawbacks of effluent treatment with conventional evaporation processes are: High operation costs (high energy consumption) High capital costs especially in corrosive environment, where noble materials are required Problems with scaling and fouling - difficult to control with varying feed quality Steam and cooling water requirement of steam operated evaporator systems Result: Evaporation has not yet been widely applied! 12

13 NEW EVAPORATION TECHNOLOGY USING LOW COST POLYMERIC FILMS AS HEAT TRANSFER AREA 13

14 NEW POLYMERIC FILM EVAPORATION TECHNOLOGY 1 Low cost Evaporative surface o large heat transfer surface o small temperature difference o low energy use - typically 8 to 14 kwh per m 3 of purified water Efficient production of polymeric heat exchanger elements by new machine (1,5 million m 2 /year) Costs only a fraction of metallic ones Q = U x A x DT P Fan = C x MF x DT 14

15 COST OF SOME HEAT EXCHANGER MATERIALS Material Relative cost/m 2 AISI x 1,0 mm tube (50 EUR/m 2 ) SMO 51 x 1,25 mm tube 2,5 654 SMO 51 x 1,25 mm tube 4,9 Sanicro x 1,8 mm tube 5,7 Hastelloy C x 1,0 mm tube 13 Titanium 50,8 x 0,9 mm tube 13 Polyolefin film 40 my (0,3 EUR/m 2 ) 0,006 High tech plastic film 0,06 15

16 NEW POLYMERIC FILM EVAPORATION TECHNOLOGY 2 Polymeric surface corrosion resistant less scaling flexible - easy cleaning Mechanical Vapor Recompression Principle (MVR) minimal steam or cooling water required Simplified Vapor Compressor (Fan) Design low operating speeds reliable easy maintenance Also multi-effect (ME) systems using waste heat or solar 16

17 POLYMERIC EVAPORATIVE HEAT EXCHANGER CARTRIDGE The heart of the system 50 elements Surface area 200 m 2 Total weight 50 kg

18 OPERATION PRINCIPLE VACUUM VESSEL LIQUID DISTRIBUTION IMPELLER LOW SPEED VAPOR COMPRESSION FAN SHAFT SEALING COMPRESSED VAPOR CONDENSATION INNER SURFACE VA PO R INLET FALLING FILM EVAPORATION OUTER SURFACE CONDENSATE COLLECTION VACUUM PUMP CONDENSATE TA NK CIRCULATION WATER CLEAN WATER FEED SOLUTION CONCENTRATE 18

19 TYPICAL EVAPORATOR LAY OUT (14 CARTRIDGES) Large diameter unit (3,8 m)

20 CONTAINER SIZE EVAPORATOR (10 CARTRIDGES) Small diameter unit 2,4 m

21 MVR-FAN 21

22 TYPICAL APPLICATION AREAS Textile industry Steel and metal industry Mining industry Pulp & Paper Food and feed industry Landfill leachate Groundwater remediation Seawater desalination Chemical industry Electronic industry Power plants Pharma industry 22

23 REFERENCE PLANTS More than 40 plants already operating in India and Gujarat, several other plants elsewhere in the world... Some examples... 23

24

25 Internal Arrangement

26 TEXTILE WASTE WATER 3 X 500 M 3 /D 26

27 METAL INDUSTRY WASTE WATER 200 M 3 /D 27

28 COMPARISON OF 1000 KLD ZLD ETP+RO+ZLD V/s MVRE+MEE UNIT MVRE + MEE ETP + UF + RO + MEE SAVING OPERATING COST Rs/M MANPOWER COST Rs/M SPACE M2 1,890 3,000 1,110 CAPITAL COST Rs 10 Cr. 12 Cr 2 Cr.

29 EFFLUENT FREE COPPER CABLE MANUFACTURING 350 M 3 /D Pickling basin Rinsing counter current Passivation Copper cable H 2 SO 4 Surface active agent Finished product Evaporator Comment by owner: "The low energy consumption is spectacular and real. Thanks to this system, we've decreased overall factory energy consumption, while increasing our production rate and our product quality." Condensate Concentrate Sulfuric acid H 2 SO 4 Capacity 350 t/d Condensate recovery 98% Conductivity 50 µs/cm Electrolyse Copper

30 MULTI EFFECT EVAPORATION USING WASTE HEAT 30

31 Boiler 5 MW 90 C Solar Collectors m 2 Boiler for back up 250 m 3 /h Vapor 65Cº Flash Cooler Solar powered ME Evaporator - Simplified Flow Diagram m 3 /d clean water 6-Effect ME Falling Film Evaporator Condenser 40ºC 1. Effect 2. Effect 3. Effect 4. Effect 5. Effect 6. Effect Cooling water 30ºC Tank Condensate 2000 m 3 65/63ºC 63/61ºC 61/58ºC 58/55ºC 55/51ºC 51/46ºC 42 m 3 /h 90ºC 80ºC 55ºC 4,7 MW 118 m 3 /h 45ºC 118 m 3 /h 1 MW of solar heat produces appr. 9 m 3 /h of clean water Concentrate 42 m 3 /h Feed 84 m 3 /h

32 RO & EVAPORATION PRIMARY TECHNICAL DIFFERENCES RO no fouling allowed! low final concentration very good pretreatment needed salt separation 95 98% limited ph & temperature if leaking -> to clean water electricity powered lower investment cost Evaporation fouling (scaling) can mostly be handled high final concentration only coarse pretreatment needed, if any salt separation > 99,9% no ph & temperature limits if leaking -> to dirty water steam & waste heat or electr. powered higher investment cost RO + Evaporation may be a good combination, but evaporation alone provides often the simplest solution!

33 NEW TECHNOLOGY COST COMPARISON TO CONVENTIONAL EVAPORATION ( LARGE EVAPORATORS ) Energy consumption (el = 6 Rs/kWh, steam 1 Rs/kg) New technology MVR (12 kwh/m kg steam/m 3 ) 82 Conventional MVR (25 kwh/m kg steam/m 3 ) 170 Conventional ME 1 stage (2 kwh/m kg steam/m 3 ) 1112 Conventional ME 4 stage (3 kwh/m kg steam/m 3 ) 298 Rs/m 3 clean water Relative investment cost Relative Low corrosion (incl. sea water) 0,7 0,9 Medium corrosion 0,6 0,8 High corrosion (high chloride, acids) 0,4 0,5 33

34 CONCLUSIONS Evaporation in general: Almost only tool for zero discharge systems Evaporation is the most powerful for removal of dissolved pollutants (salts, organic matter etc.) But costs are high in conventional evaporators MVR reduces operation costs Scaling and fouling may be a problem New Polymeric Film technology: Investment and operation costs are considerably reduced Scaling and fouling problems are more easily managed Recycling of surprisingly dilute effluent streams is becoming feasible Waste heat or solar can be efficiently utilized (ME) 34

35 ADDITIONAL INFORMATION For any queries, pl. call Mr. Chandan Kumar, Cell: Arvind Mills Premise. Arvind Envisol Ltd Naroda Raod Ahmedabad 35

36 36