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 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!