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Biodiesel Production : Part 2 Product Recovery. Renewable Products Development Laboratories Portland, Oregon, USA. Product Recovery Steps. Ester – Glycerol Separation Ester Washing and Drying Glycerol Recovery Methanol Management Wastewater Considerations. Ester – Glycerol Separation.
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Biodiesel Production : Part 2Product Recovery Renewable Products Development Laboratories Portland, Oregon, USA
Product Recovery Steps • Ester – Glycerol Separation • Ester Washing and Drying • Glycerol Recovery • Methanol Management • Wastewater Considerations
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
Ester Washing • Primary purpose – removal of soaps • Secondary purposes: • Removal of free glycerol • Removal of catalyst residues • Removal of trace methanol
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.
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
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 > 50 C
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.
Methanol Management • > 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.
Wastewater Considerations • Typical processes use about 1 gallon of water for each gallon of biodiesel. • All water should be softened to < 1 grain hardness. • Soapy washwater contains about 25,000 ppm BOD5. • Soapy washwater usually has pH 7.5 to 9.0
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!