Vedanta aluminium ltd reverse osmosis process

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Vedanta aluminium ltd reverse osmosis process

  1. 1. Engineering Excellence Awards 2013 “Reverse Osmosis in Aluminium Smelter for Effluent Treatment” Vedanta Aluminium Limited, Jharsuguda 1
  2. 2. Domestic Aluminium Smelter Scenario Production in KTPA Balco (expansion) 325 Balco Next 5 years Forecast Production Projections: 245  Aluminium demand remains healthy Nalco 460 Lapanga (Hindalco) Vedanta Plant1 Vedanta Plant2 359 Mahan Aluminium Hirakud (Hindalco) Renukoot (Hindalco) 213 Muri (Hindalco) Muri (Hindalco) 359 Renukoot (Hindalco) 400 Mahan Aluminium 359 Hirakud (Hindalco) Lapanga (Hindalco) Nalco Balco  As per the current greenfield projects, Aluminium Production is set to be doubled by next 5 years  Water consumption rate is approximately 1m3/MT of Al produced. Efficient recycling techniques required Balco (expansion) Vedanta Plant2 1100 Vedanta Plant1 500 0  The raw effluent coming from the plant contains up to 50 ppm fluoride 500 1000 1500 In Production – 1918 KTPA Greenfield – 2402 KTPA 2
  3. 3. Smelter Process Scenario Cast Metal Air Emission Raw Material Aluminium Smelter + Power Solid Waste Waste Water Raw Material Alumina: Al2O3 Carbon Anode: C Cryolite: Na3AlF6 Aluminium Fluoride: AlF3 Raw Effluent 3
  4. 4. Major Objectives of Effluent Treatment  Zero discharge of rejected effluents to ambient water  Treating effluents to fresh water levels. Hence Conservation of water 4
  5. 5. Types of Effluent Treatment Techniques Nalgonda Technique Adsorption Technique Reverse Osmosis Ion Exchange Method Distillation Process 5
  6. 6. Why Reverse Osmosis ?? Fluoride removal efficiency > 99% Membrane Separation Technology without using Chemicals Less area for operation Removes other biological impurities 6
  7. 7. Process flow diagram of Effluent Treatment Plant 50 50 7
  8. 8. Preliminary Treatment Rated Capacity: 100m3/hour x 3  The effluent recycling plant is designed to treat 250 m3/day of effluent.  The rejects of the ETP are disposed of to a sludge drying bed by back flush in the system. The sludge is further disposed off in SLF area. 8
  9. 9. Sand Filtration and Iron Removal Pressure Sand Filter Rate : 50 m3/hour It is used to remove the suspended solids in the effluent Iron Removal Filter Rate : 50 m3/hour It is used to remove the iron particles in the effluent 9
  10. 10. Ultrafiltration & Double Stage RO Ultra Filtration Rate: 50 m3/hour The mesh size of RO membrane is 0.01 microns  UF consists of hydranautics membrane fitted with PLC based system for automatic service.  The main function of this system is to reduce BOD, COD, biological impurities, suspended solids and oil from the effluent. 10
  11. 11. Treatment by Reverse Osmosis Principle of Reverse Osmosis
  12. 12. Double Stage RO Reverse Osmosis Rate: 50 m3/hour The mesh size of RO membrane is 0.0001 microns  RO typically operates at 10-12 bar for reverse high pressure.  The membranes of RO are semi-permeable.  It consists of double stage membrane to reduce dissolve impurities and fluoride from the effluent. 12
  13. 13. RO Membranes Maximum Operating Temperature – 30 – 35 oC Life Span – 3 Years  RO membranes are cellulose acetate, aromatic polyamide and thin film composite (TFC). In general all TFC membranes are placed in series in a pressure vessel  Cellulose acetate is resistant to small concentration of chlorine and is therefore kept free from bacteria and its subsequent re-growth.  Aromatic polyamide cannot tolerate chlorine but is resistant to bacteria. It is useful in treating over a wider pH range (4-11) of effluent.
  14. 14. Treated Effluent Quality Effluent Sand & Iron Removal TSS < 1255ppm 7.3 – 8.1 pH Ultra Filtration TSS < 5.0 ppm 7.0 – 7.5 pH TSS pH Reverse Osmosis < 1.0 ppm 7.0 – 7.5 TSS pH < 0.1 ppm 7.0 – 7.5 BOD < 30 ppm BOD < 20 ppm BOD < 5 ppm BOD < 5 ppm COD < 100 ppm COD < 90 ppm COD < 30 ppm COD < 20 ppm O&G < 35 ppm O&G < 5 ppm O&G < 2 ppm O&G < BDL TDS < 500 ppm TDS < 500 ppm TDS < 500 ppm TDS < 50 ppm Fluoride < 50 ppm Fluoride < 7 ppm Fluoride < 5 ppm Fluoride < 1ppm Iron < 2.4 ppm Iron < 0.3 ppm Iron < 0.2 ppm Iron < 0.1 ppm Hardness < 120 ppm Hardness < 120 ppm Hardness < 120 ppm Hardness < 5 ppm Raw Effluent ETP + PSF + IRF After Ultra Filtration After Reverse Osmosis 14
  15. 15. Water Consumption Scenario 3 700000 598907 584141 600000 2.64 500000 2 2.13 410563 400000 1.74 303833 300000 1.3 1.23 1 0.85 200000 90553 0 100000 0 0 2008-09 2009-10 2010-11 Recycled Water 2011-12 2012-13 2013-14 (YTD) SWC 15
  16. 16. Handling of RO Rejects – Solar Pond Specifications of Solar Pond Surface Area – 2000 m2 Tank Depth – 2 meters Free Board – 0.25 meters Evaporation rate – 5m3/hour  Solar pond is used for forced evaporation of rejected RO effluents  It consist of rectangular concrete tank fitted with specially designed solar air heating system and mist fans 16
  17. 17. Solar Panels & Atomizers Mist Fans (atomizers) Solar Heating Panels Mist Fans Solar Heating Panels  The RO reject gets converted into mist by mist fans.  They are used to blow hot air to the solar pond  It is then evaporated by blowing hot air with solar air heating system  It ensures faster evaporation in spite of being spread over a small surface area. 17
  18. 18. Disposal of Rejected Effluents HAZARDOUS WASTES SLF 18
  19. 19. Power Consumption Total Power connected load is 93.2 KW Total Power consumption is 2236.8 KWH per day 19
  20. 20. Benefits of Advanced Solar Pond Multiple Effect Evaporator Normal Solar Pond m2 Advanced Solar Pond 2000 m2 with a depth of 2m Surface area - O & M cost Rs 43/m3 Rs 28.9/m3 Rs 10/m3 Evaporation Rate 3.2 m3/hour 3.3 m3/hour 5 m3/hour 19200 20
  21. 21. Key Benefits 100% recycling of water coming in to the system Consistency in output quality even with varying inputs It reduces fluoride to < 1 ppm as well as other pollutants significantly Can be used to treat any fluoride contaminated water If adopted by all smelter plants as per present scenario, this can reduce approximately 2 Mt fluoride load to Environment over conventional treatment 21
  22. 22. Our Vision is to become the Benchmark in Environmentally Sustainable Aluminium Smelter 22

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