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Engineering Excellence Awards 2013
“Reverse Osmosis in Aluminium Smelter for Effluent Treatment”
Vedanta Aluminium Limited, Jharsuguda
1
Domestic Aluminium Smelter Scenario
Next 5 years Forecast
Production Projections:
Aluminium demand remains healthy
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
The raw effluent coming from the plant contains up to 50 ppm fluorideVedanta Plant1
Vedanta Plant2
Mahan Aluminium
Renukoot (Hindalco)
Muri (Hindalco)
Hirakud (Hindalco)
Lapanga (Hindalco)
Nalco
Balco
Balco (expansion)
020
040
060
080
010
0012
00
500
1100
359
400
359
213
359
460
245
325
Production in KTPA
Production in KTPA
2
In Production – 1918 KTPA
Greenfield – 2402 KTPA
Raw Material +
Power
Raw Material
+
Power
Raw Effluent
Raw Material
Alumina: Al2O3
Carbon Anode: C
Cryolite: Na3AlF6
Aluminium Fluoride: AlF3
Smelter Process Scenario
3
Major Objectives of Effluent Treatment
Treating effluents to fresh water levels. Hence Conservation of water
Zero discharge of rejected effluents to ambient water
4
Nalgonda Technique Adsorption Technique Ion Exchange Method
Reverse Osmosis Distillation Process
Types of Effluent Treatment Techniques
5
Fluoride removal efficiency > 99%
Membrane Separation Technology without using Chemicals
Less area for operation
Removes other biological impurities
RO
Why Reverse Osmosis ??
6
Process flow diagram of Effluent Treatment Plant
50
50
7
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
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
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.
Treatment by Reverse Osmosis
Principle of Reverse Osmosis
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.
RO Membranes
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.
Maximum Operating Temperature –
30 – 35 oC
Life Span – 3 Years
Sand & Iron Removal Ultra Filtration Reverse Osmosis
TSS < 1255ppm
pH 7.3 – 8.1
BOD < 30 ppm
COD < 100 ppm
O & G < 35 ppm
TDS < 500 ppm
Fluoride < 50 ppm
Iron < 2.4 ppm
Hardness < 120 ppm
TSS < 5.0 ppm
pH 7.0 – 7.5
BOD < 20 ppm
COD < 90 ppm
O & G < 5 ppm
TDS < 500 ppm
Fluoride < 7 ppm
Iron < 0.3 ppm
Hardness < 120 ppm
TSS < 1.0 ppm
pH 7.0 – 7.5
BOD < 5 ppm
COD < 30 ppm
O & G < 2 ppm
TDS < 500 ppm
Fluoride < 5 ppm
Iron < 0.2 ppm
Hardness < 120 ppm
TSS < 0.1 ppm
pH 7.0 – 7.5
BOD < 5 ppm
COD < 20 ppm
O & G < BDL
TDS < 50 ppm
Fluoride < 1ppm
Iron < 0.1 ppm
Hardness < 5 ppm
Effluent
Raw Effluent ETP + PSF + IRF After Ultra Filtration After Reverse Osmosis
Treated Effluent Quality
14
2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 (YTD)0
1
2
3
0
100000
200000
300000
400000
500000
600000
700000
0
90553
410563
598907 584141
303833
2.64
2.13
1.74
1.231.3
0.85
Recycled Water SWC
Water Consumption Scenario
15
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
Solar Panels & Atomizers
Solar Heating Panels
They are used to blow hot air to the solar pond
It ensures faster evaporation in spite of being spread over a small surface area.
Solar Heating PanelsMist Fans (atomizers)
Mist Fans
The RO reject gets converted into mist by mist fans.
It is then evaporated by blowing hot air with solar air heating system
17
HAZARDOUS WASTES
Disposal of Rejected Effluents
SLF
18
19
Power Consumption
Total Power connected load is 93.2 KWTotal Power consumption is 2236.8 KWH per day
Evaporation Rate
Benefits of Advanced Solar Pond
Multiple Effect Evaporator Normal Solar Pond Advanced Solar Pond
- 19200 m2 2000 m2 with a depth of 2m
Rs 43/m3 Rs 28.9/m3 Rs 10/m3
3.2 m3/hour 3.3 m3/hour 5 m3/hour
O & M cost
Surface area
20
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
Our Vision is to become the Benchmark in Environmentally Sustainable Aluminium
Smelter22