Ultra energy

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Seawater Desalination by Ultralow-Energy Reverse
Osmosis
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• Abdul Haseeb

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Reverse Osmosis
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Reverse osmosis (RO) is a water purification
technology that uses a semipermeable membrane to
remove ions, molecules, and larger particles from
drinking water. In reverse osmosis, an applied
pressure is used to overcome osmotic pressure.
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Osmotic Pressure
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• the measure of the tendency of a solution to take
  in water by osmosis

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Spiral-wound Element
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• Spiral-wound Element refers to a membrane
  configuration which is comprised of
• Flat sheet membrane permeate channel spacer
• Flat sheet membrane feed channel spacer
• combination rolled up around a product collection
  tube.

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Early Research
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• 1950s and 1960s University of Florida
• semipermeable reverse osmosis (RO) membrane
• thick-film
• asymmetric
• cellulose acetate
• Pressure required up to 105 bars

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Limitations
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• selectivity of membranes
• osmotic pressure of the seawater
• Recovery 25
• Energy Required 10 kWh/m3.

• GOAL Cost Effective Technology to desalt sea
  water for human consumption.

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Thin-Film Composite Membranes
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• 1970
• thin-film composite membranes using polymeric
  materials
• Polyetherurea
• Polyamide
• Reduced resistance
• Pressure less than 70 bars
• Recovery 35
• Energy 6.6 kWh/m3

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First Commercial SWRO
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• 1978 Jeddah, Saudi Arabia
• Design Parameters
• Capacity 12,000m3/day
• Operating Pressure 56 bars
• Recovery 30
• TDS 1000mg/L (Blending with 50mg/L condensate)
• Energy 6.1 kWh/m3

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SWRO Energy Reduction using Energy Recovery
Technology
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• Pelton Wheels - 100-year-old engineering concept
• SWRO high-pressure pump/motor assemblies 1982
• Pelton wheel RO flow scheme

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Pelton Wheel Characteristics
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• Low capital cost
• Directly connected to SWRO pump/motor
• Requires full-sized SWRO pump/motor
• Operates in a centrifugal mode follows flow
  pressure curves
• Overall net transfer efficiencies can reach 88
• Metallic construction

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Efficiency Curve
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• Current Pelton wheel devices overall Net
  Transfer Efficiency 60-88
• Typical Pelton wheel efficiency
  curve

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Turbochargers
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• Improvement in economy Energy Recovery
  Technology
• A stand-alone device
• Not connected to the high-pressure pump
• Employed in Variety of ways

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Typical turbocharger RO flow scheme
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Turbocharger as a Booster Pump
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Turbocharger Characteristics
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• Moderate capital cost compared to Pelton wheel
• Not connected to SWRO pump/motor assembly
• Operates in a centrifugal mode and follows flow
  and pressure curves
• Overall net transfer efficiency follows a curve
  and can reach 83
• Metallic construction
• Can be used in a variety of flow schemes

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Efficiency Curve
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• Efficiency 60-70
• The highest overall net transfer efficiency
  achieved by a turbocharger is 83

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SWRO Energy Optimization
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• The three areas of innovation are
• Membrane/element design
• 1978 15 m2 of membrane 7.5 m3 of permeate/day
  98.6 salt rejection
• Today 40 m2 of membrane 28-34 m3 of
  permeate/day 99.75 salt rejection
• Large-capacity high-pressure pump/motor
  efficiency
• Energy recovery technology improvements

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Historical Cost Comparison

• Reduction in Energy Consumption
• 10 kWh/m3 - late 1970s
• 3.5 kWh/m3 2000

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Achievements

• Affordable Desalination Collaboration (ADC) -
  California report published in August 2006
• Recovery 42.5
• Energy 1.58 kWh/m3
• TDS 110mg/L
• Efficiency 95

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