Biodiesel Production : Part 2 Product Recovery

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Biodiesel Production Part 2Product Recovery

• Renewable Products Development Laboratories
• Portland, Oregon, USA

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Product Recovery Steps

• Ester Glycerol Separation
• Ester Washing and Drying
• Glycerol Recovery
• Methanol Management
• Wastewater Considerations

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Ester Glycerol Separation

• Separation is based upon Ester-Glycerol
  immiscibility and density difference.
• Separation is affected by
• Glycerol dispersion in ester phase
• Presence of mono-, di-, triglycerides
• Presence of un-reacted alcohol
• pH of the two phases

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Ester Washing

• Primary purpose removal of soaps
• Secondary purposes
• Removal of free glycerol
• Removal of catalyst residues
• Removal of trace methanol

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Ester Wash Methods

• Use warm ( 120 F), soft water
• Water should be free of iron and copper to
  improve stability.
• Use gentle washing action to avoid creating
  emulsions.

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Ester Drying

• Esters can have 1500 ppm dissolved water.
• Washing can add entrained water up to 2 w/w
• Can dry esters by using
• Spray drying
• Vacuum dryng
• Evaporators
• Absorbents

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Glycerol Recovery

• Recover methanol by spray drying
• Neutralize catalyst using mineral acid
• Can remove catalyst using ion exchange
• All glycerol processing should take place at gt 50
  C

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Glycerol Uses

• Glycerol is one of the most versatile chemical
  feedstocks.
• Glycerol is easily derivatized.
• Glycerol is a fermentation substrate.
• Glycerol decomposes at 290 C into acrolein
  and/or other materials.

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Methanol Management

• gt 98 methanol recycle is the goal
• Methanol affects all product recovery operations
• Methanol emissions in air and water are major
  issues in permitting and safety.

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Wastewater Considerations

• Typical processes use about 1 gallon of water for
  each gallon of biodiesel.
• All water should be softened to lt 1 grain
  hardness.
• Soapy washwater contains about 25,000 ppm BOD5.
• Soapy washwater usually has pH 7.5 to 9.0

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Summary

• Biodiesel production is deceptively difficult.
• Multiple production approaches lend themselves to
  multiple scales of production.
• It is NOT biodiesel until it meets ASTM 6751!